To someone new to the instrument, trying to choose a guitar can be a daunting task. Fortunately, if you take the time to learn some basics you can make the experience a lot less frustrating, maybe even enjoyable. Guitars can be broken down into three distinct categories. If you narrow your choice down to one of these categories, you're over halfway there!
Acoustic guitars have a large hollow body, and a round sound hole, and are strung with steel strings. The wonderful thing about acoustic guitars is their simplicity. You don't need an amplifier or any other equipment. You just take the instrument out of the case and play. You can bring it to the backyard, or the beach, or sing-alongs around a campfire . Acoustic guitars are most often associated with country, blues, and folk music, but they have been used in a lot of rock, and other styles. If you want an instrument to play casually, or to accompany your voice. This is probably the guitar for you. If you plan on performing in the future consider one of the many acoustics that are available with an electronic pickup system. This allows it to be plugged into an amplifier or P.A. system. Most guitarists who play electric guitars have an acoustic also. So, if you change over to electric in the future you'll probably keep your acoustic as well.
Classical Guitars have a hollow body, and a round sound hole similar to a standard acoustic, however they are designed to be strung with nylon strings. They are most often associated with Classical or Flamenco styles. They are also found in traditional music from South America. Unless you plan on playing one of these styles, this is probably not the instrument for you. It should be noted that a classical guitar should never be strung with steel strings. It will result in serious damage.
Electric guitars have a solid wood body and steel strings. The use a magnetic pickup on the body of the guitar to change the vibration of the strings into an electronic signal that is sent through a cable to an amplifier. The great thing about an electric guitar is the ability to change the tone. With the turn of a knob or two, you can go from a smooth clean jazz sound, to a distorted heavy metal tone.
There are countless varieties of electric guitars on the market, but historically the most popular style has been the Fender Stratocaster. This versatile instrument has remained virtually unchanged since the 1950's and has been used in countless recordings. There are decent quality copies available in all price ranges, made by numerous manufacturers. If you prefer a "fatter" sound you might look at something modelled after Gibson's Les Paul model. Second only in popularity to the Stratocaster, this instrument has thousands of loyal fans. There are also copies available to fit any budget.
When you choose a guitar its an individual decision. Do some research. Decide how much you want to spend. Take your time and find something you like. If you make the right decision you'll end up with something that will you pleasure for years to come.