“I don’t read your magazine anymore,” says my 36-year-old sister as we ride in a rental car. “I don’t read your magazine anymore because all you guys ever write about is emo, and I don’t get it.”

Now, for a moment, I find myself very interested in what my sister is saying. I absolutely cannot fathom what she could possibly hate about emo, and (I suspect) this subject might create an interesting ten minutes of rental-car discussion. Does she find emo too phallocentric? Do the simplistic chord progressions strike her as derivative? Why can’t she relate to emo? I ask her these questions, and I await her answer. But her answer is not what I expect.

“No, no,” she says. “When I say I don’t get emo, I mean I literally don’t know what it is. The word may as well be Latin. But I keep seeing jokes about emo in your magazine, and they’re never funny, because I have no idea what’s supposed to be funny about something I’ve never heard of.”

This, of course, leads to a spirited dialogue in which I say things like “‘Emo’ is short for emotional,” and she says things like “But all pop music is about emotions,” and I respond by saying, “It’s technically a style of punk rock, but it’s actually more of a personal, introspective attitude,” and she counters with “That sounds boring,” and then I mention Andy Greenwald (author of Nothing Feels Good: Punk Rock, Teenagers, and Emo), and she asks, “Wasn’t Andy Greenwald a defensive end for the Pittsburgh Steelers in the late ’70s?” and I say, “No, that was L.C. Greenwood, and I’m pretty sure he doesn’t know any of the members of Senses Fail.”

But anyway, I learned something important from this discussion: that reading rock magazines must be very confusing to people who only listen to rock music casually. Whenever journalists write about music, we always operate under the assumption that certain genres are self-evident and that placing a given band into one of those categories serves an expository purpose. Just as often, an artist will be described as a synthesis of two equally obscure subgenres, and we’re all supposed to do the sonic math ourselves. However, this only helps the informed; that kind of description is useful to those who have already conquered the rock lexicon. What we need is a glossary of terms so we can all share an equal playing field.

I will do my best.

DISCO METAL: This is up-tempo, semiheavy guitar rock that someone (usually a stripper) could feasibly dance to. White Zombie made a lot of songs in this style. Weirdly, it does not seem to apply to straightforward metal bands (Kiss, Van Halen) who overtly write disco songs (“I Was Made for Lovin’ You,” “Dance the Night Away”). No one knows why.

SHOEGAZE:Music by artists who stare at their feet while performing—presumably because they are ashamed to be playing such shambolic music to an audience of weirdos.

POST-ROCK: This is when a group of rock musicians employ traditional rock instrumentation to perform music for people who traditionally listen to rock—except these musicians don’t play rock and the songs don’t have any vocals. I don’t get it either. The premier band of this genre is Tortoise, and the kind of people who like post-rock are the same kind of people who think it’s a good idea to name a band Tortoise.

PSYCH: (as in “psychedelic”) The modifier psychhas only recently come back in vogue, which is interesting. You have possibly heard the terms “psych folk” (sometimes applied to artists in the vein of Devendra Banhart) or “psych country” (which is vaguely similar to what used to be called “outlaw country”) or “psych rock” (which is what Courtney Taylor of the Dandy Warhols calls his band’s sound in the documentary DIG!). I’ve made a great effort to try to find the unifying principle among these permutations of psych music, and the answer is probably what’d you expect: This is music for drug addicts, made by drug addicts. If you are in a Tejano quartet and all four of you start taking mescaline (and if all the kids who come to your shows drop acid in the parking lot before entering the venue), you now play “psych Tejano.” That’s the whole equation.

GRIME: Almost two years ago, I asked two learned people at Spinto explain to me what grime is. They both said, “Don’t worry about it. You will never need to know. It’s completely unnecessary knowledge.” Then, over the next few weeks, grime came up in conversation on three separate occasions. And it would always come up in the same manner: Someone would mention either Dizzee Rascal or the Streets, refer to them as grim artists, and immediately be told, “Those aren’t real grime artists. That’s not real grime.” As such, this is all I know about grime—it’s British rap (but not really) that is kind of “like garage and 2-step” (but the word garage is pronounced like marriage), and it’s supposedly a reflection of life in lower-class London neighborhoods like Brixton. If anyone out there knows what grime is, e-mail me at cklosterman@spin.com. But make sure you write “This is about grime” in the subject line so I will know to ignore it completely.

FASHION ROCK: The concept of fashion rock revolves around (a) appearing to be impoverished while (b) spending whatever little money you possess on stylish clothing (and possibly cocaine). In short, fashion rockers aspire to look like superfancy hobos, which is obviously nothing new (this look was called “gutter glam” by L.A. hair bands in the 1980s and “mod” by British goofballs in the late 1960s). What’s curious, however, is that fashion rock—though defined by clothing—does seem to have an identifiable sound, which is a kind of self-conscious sloppiness that translates as a British version of the Strokes (this is best illustrated by the Libertines, but even more successfully by the Killers, possibly because they are not even British).

RAWK: This is how people who start bands in order to meet porn stars spell rock. It is also applied to long-haired guitar players who can’t play solos.

PROG: There was a time when “progressive rock” was easy to define, and everybody knew who played it—Jethro Tull, ELP, Yes, and other peculiar, bombastic men who owned an inordinate number of Moog synthesizers during the mid-1970s. This was an extremely amusing era for rock; the single best example from the period was King Crimson’s 1969 song “21st Century Schizoid Man,” a track built on a spooky two-pronged premise: What would it be like to encounter a fellow who was not only from the distant future, but also suffering from an untreated mental illness? At the time, “21st Century Schizoid Man” was the definition of progginess. However, just about anything qualifies as prog in 2005. An artist can be referred to as “kind of proggy” if he or she does at least two of the following things: writes long songs, writes songs with solos, writes songs about mythical creatures, writes songs that girls hate, grows a beard, consistently declines interview requests, mentions Dream Theater as an influence, claims to be working on a double album, claims to be working on a rock opera, claims to have already released a rock opera, appears to be making heavy metal for people who don’t like heavy metal, refuses to appear in his or her own videos, makes trippy music without the use of drugs, uses laser technology in any capacity, knows who Dream Theater is.

MUSK OX ROCK: Combining woolly ’90s grunge with the ephemeral elasticity of Icelandic artists like Björk and Sigur Rós, so-called oxenheads deliver thick, nurturing power riffs that replicate the experience of melting glaciers, troll attacks, and political alienation. The genre includes bands such as Switchfoot, Radiohead, and Bettie Serveert.

IDM:This is an acronym for “Intelligent Dance Music.” Really. No, really. I’m serious. This is what they call it. Really.