When a copyrighted song is put on a sound carrier (such as a record, tape, CD) or in a digital file for the purpose of online music distribution, that is an exercise of the reproduction right of the song.
When your song is reproduced in this manner, you are owed mechanical royalties on each copy. You also earn mechanical royalties when your music is used on streaming platforms. These royalties are collected and distributed to publishers by societies such as The Harry Fox Agency (USA), and CMMRA (Canada), as well as many others globally.
It is also worth noting that the reproduction right is engaged whenever a copyrighted song is embodied in an audiovisual production (such as a film, television program, or commercial), known as a "sync".
When a copyrighted song is played on the radio or television, or performed in a theatre or concert, that’s an exercise of the performance right in the song. The royalties generated in these instances are performance royalties and are collected and distributed to writers and publishers by Performing Rights Organizations (PRO's).