How to see the differents between different version?

If I want to find the differents between different version?
for example: copter 3.5.3 ,copter 3.5.5,copter 3.5.6,copter 3.5.7,
another example: copter 3.5 copter 3.6 copter 3.7
what shoud I do?

thanks.

Read the release notes.