A bass is like any other instrument. It can be used to make a melody, harmonize, and you can even play solos with one (look up Cliff Burton or Flea if in doubt). The uses are only the limit of your imagination. Classical uses are for a type of basslines melody or to harmonize the rhythm lines but this isn't necessarily its only use.
A tuba is a low pitched instrument. It uses the bass clef also.
You can play any instrument with the bass clef. This is just a convention to write notes of certain height in the bass clef. You can play a piece on an instrument if their diapasons match. Or even it is not so, you can transpose a piece to the diapason for your instrument. Usually, pieces written for bass instruments (for example, electric bass guitar or double bass) are noted on the bass clef.
An instrument that starts with a b is: a bass clarinet.
The stringed bass/upright bass has the lowest register in the string family. The cello is also a bass string instrument, though it's not as low as the bass.
Bass (instrument)
Bass Guitar
There are a lot. Some of my favorites include:stringed: contrabasso (aka double bass)bass guitaroctobassbass violwhamolabrass: tubabass tromboneeuphoniumwoodwind: bassoonbaritone saxpercussion: piano (typically uses both bass clef and treble clef)timpani
A homophone for bass (the instrument) is the word base.
Trombone. Or, since you specified bass a bass trombone.
An Electric Bass is an amplified four-stringed instrument which produces low sounds. A lot of the time, the instrument will be a back-up to a more 'major' instrument in the song such as the Electric Guitar.
MUSICAL
A bass soloist is a person who performs music on the bass instrument by himself/herself.