Some basics for the beginning guitarist, or the ambitious music lover.
Some of us grew up listening to gospel. Others, bluegrass, blues, jazz, reggae or any combination of the myriad of musical styles in existence today. With the advent of nearly free media, our exposure to different musical styles is almost overwhelming, and with it is an equally stimulating exposure to sounds, voicing, and timbres that are potentially foreign.
The guitar, however, probably doesn't fall into that category. Having achieved a level of popularity surpassed only by (and it's up for debate!) the human voice, it's highly unlikely to come across anyone in our enlightened age who couldn't look at the instrument and identify it. On the other hand, unless you're dealing with someone who plays, you're likely to see them struggling with the specifics of what type of guitar they may be trying to identify. It appears in various forms, of course, for few different reasons. The primary reason being that with different types of guitar, you naturally get different types of sounds.
*It's important to note that there are variations within these types of guitars; much like there are variations of automobile styles. This is a basic outline covering the most popular variants.
The classical guitar: This is where it all began. This style has been around for centuries and we still see it used today, though the manufacturing process, like anything else, has progressed with technology. Sparing the details of the hows and whys, suffice to say that this type of guitar once featured strings made from ox or sheep gut (how far we've come). Known for its mellow, warm sound-attributed to its nylon/silver wound strings on a hollow body-this variation can be found in a wide range of music genres, everywhere from classical to folk to jazz. It also features a wider neck and subsequently wider string spacing to accommodate for fingerpicking, as it's uncommon to see this type of guitar played with pick.
The acoustic guitar- More common in modern-day than the classical guitar, the primary differences are the string material used (phosphor bronze, though they're often called "steel strings"), generally a slimmer neck, a hollow but considerably larger body, and though it's common to see, it's most frequently strummed with a guitar pick. Think Johnny Cash, Garth Brooks, Johnny Rzeznik, Emmilou Harris and the like. Strum one of these, and you're bound to notice a big, robust, and shimmering sound, assuming the strings are reasonably new.
The electric guitar: Certainly the youngest variant, the electric guitar and its innovators all but single-handedly changed the course of music. Born out of necessity, the electric guitar came about to solve the issue of volume that accompanied the acoustic guitar. By outfitting the instrument with a "pickup" (a device that converts string vibration into an electromagnetic signal), greater volumes could be achieved by coupling the guitar with an amplifier via a cable. The electric guitar's beginning was a bit more modest than the aggressive, noisy (according to some) tones dialed in today. Suffice to say that it's the most flexible in terms of voicing, easier on the fingers (assuming a good "setup"-basic maintenance- is done) due to its thinner strings, features a thinner and normally solid body, and slimmer neck than its predecessors and is therefore a great option when learning how to play guitar.
The bass guitar- A specially designed type of guitar, this variant functions primarily in a support role and most commonly in a band or group setting. At the risk of sounding musically narrow, a bass guitar covers the bottom end of the sound spectrum in a musical climate, a guitar (any of the above types) tends toward the midrange and higher end of the spectrum. As always, you're bound to see deviations from this rule of thumb in the interest of pursuing musical innovation (think Flea from Red Hot Chili Peppers). Much like the guitar, the first versions of this instrument were hollow and enormous and later adapted to be amplified. The strings are much thicker than a guitar's, the neck is considerably longer and, as there are customarily 4 or 5 of them, the necks tend to be slimmer.
These are easily the different types of guitars you're bound to come across at your local music store, or see on MTV if you happen to accidentally catch a music video. Are there others? Certainly, which will be covered at a later time. Baritone guitars, 12 string acoustics/electrics, 7 and 8 string guitars, 6, 7, and 8 string basses, etc, to name a few.