Who are they and what do they do? The composer composes music, in other words writes scores which are played by musicians. A composer can work with a recording company. Mostly s/he or she cooperates directly with singers and other musicians.
What are the activities of the job? Composing music according to your own ideas or with reference to a commission from the person or organisation requiring the music; cooperating with songwriters or librettists if the music is to involve vocal performance; creating a score; testing it with musical instruments; possibly rehearsing it with an orchestra or choir or other group of performers..
Where is it done and under what conditions? A composer can usually work wherever s/he prefers (at home, in a studio, outdoors etc.) when actually composing. When the music is played, work may take place in a studio or concert hall etc.
What tools/equipment do they use? Paper, pencil, metronome, musical instruments.
What do you need to succeed? Apart from talent, a composer should have graduated from a school of music, or from a university that specialises in the theory or history of music. A composer should also know to play a musical instrument.