What are mechanical royalties?

Digital shops pay for every sold / streamed song 10% over the gross sale to the PRO (or direct to the publisher USA / Latin America only). The PRO (or the publisher USA / Latin America only) will distribute this amount to all the songwriters that have written the song.

Example: So when iTunes sells a song for 1 Euro, 0.10 Euro will be paid directly to the PRO (or direct to the publisher USA / Latin America only). This 0.10 Euro will be split and distributed by the PRO (or the publisher USA / Latin America only) to the songwriters that have written the song. This is called: mechanical royalties.