Boku is one way of saying I.

There's many different ones, each carrying different connotations, and some tied to a certain gender. After studying Japanese for a while, I decided 'boku' probably suited me best.

Some of the differences between the pronouns are hard to explain, but you get a good feel for their various tones and connotations simply by hearing them used in movies and suchlike.
Wa is a particle that marks the subject of a sentence. Particles mark the word directly before them, so 'Boku wa' is like 'As for me...'.

So yep, you're more or less right.
