Typically, at least in physics (but as far as I know in all sciences), it's not compensated, and the reviewers are anonymous. Some journals try to change this,

Typically, at least in physics (but as far as I know in all sciences), it's not compensated, and the reviewers are anonymous. Some journals try to change this, with some "reviewer coins", or Nature, which now publishes reviewer names if a paper is accepted and if the reviewer agrees. I think these are bad ideas. Professors are expected to review by their employer, typically, and it's a (very small) part of the tenure process.