The 2 most common types of basses are electric and upright.  Electric bass is generally used in popular music, rock and funk.  It looks like a guitar however it normally only has 4 strings and is tuned an octave lower.  If you are interested in playing rock, funk or hip-hop, this would be the instrument for you.  The upright or standup bass is more commonly used in Jazz, old time Country, Bluegrass, Rockabilly and of course classical music.