The Release Notes record what changed with each version of the Android app: new functions, improvements to existing ones and fixed faults. The newest version is at the top.
The list is most useful for two questions. First, whether something you have noticed has already been fixed – in which case an update is all it takes. Second, what changed when something looks different after an update.
Which version you are running is shown in the app itself. The current one is in the download area, and the Windows counterpart of this list is under Windows Release Notes. For questions about a particular change, see the FAQ or contact support.