Profile
Profiles are a feature on OS used since 2014 on forums, and 2015 on songs.
Pictures
Profile Pictures (commonly known as Profiles or simply PfP) is a special feature on OS that adds a special image.
Changing PfPs
To change a PfP, one should go to UserCP, change avatar, and click the upload avatar button. However, it's only around 78km (promoted as 100 pixels) to 500km.