No Compatibility: implies that with every compilation of the component, you end up with a new entry in the windows
registry i.e if you go to Project then References you would
see a new entry every time you recompile your component
for any slight changes

Project Compatibility - is what you check off when developing so that the original entry keeps being overwritten for subsequent compilations

Binary Compatibility: Once you're ready to ship the component to the users and you're ecstatic that everything works, you set that.... Now any changes you made after that
are ok UNLESS you change the methods or properties of the
component in which case you would have to recompile all the clients that talk to this component

Getting ready for the exam, R U?