Beginner's question on how to use git for multiple parallel versions

Hello all,

I’ve got a project that I want to do version management on with git but being a beginner in
cvs/svn/dvcs etc. terminology I don’t know yet how to set it up.
My project needs to exist as several parallel copies, i.e. there is a “main version” in
which I do my development but it needs to end up being available as a couple of different
configurations.
For instance, say there is a file table.xml then this needs to contain different rows for versions
A and B. Likewise, a file process.bpel needs to be named identical for each version but contain
different content depending on whether it is distributed as version A or version B. Any changes
made in non-version specific files should be visible in all copies, but changes made to
version-specific files need to remain isolated to that particular version.

I read about branching, merging, rebasing and cherry-picking commits but I don’t get it yet.
Can anyone enlighten me on how I should approach this in a way that I can maintain easily
throughout future development for my situation?

Thanks in advance for any pointers,

Best,

Chris