PRO

A Performing Rights Organization collects performance royalties on behalf of composers (includes songwriters and lyricists). The sole PRO in Canada, SOCAN, collects royalties for both the composer as well the publisher (unless assigned to an outside publisher).
American PROs include ASCAP and BMI, as well as some invite-only organizations such as SESAC.
In order to receive the composition and publishing royalties you are entitled to, your song must be registered with SOCAN, membership and song registration with SOCAN are both free.