Do I have to do something to tell Git whether some files are binary (like in Subversion)? Or, can Git handle binary data automatically? If I change the binary file, so that I have 100 binary revisions, will git just store all 100 versions individually in the repository? What are submodules for with git?

How does Git deal with binary files?

Do I have to do something to tell Git whether some files are binary (like in Subversion)? Or, can Git handle binary data automatically?
If I change the binary file, so that I have 100 binary revisions, will git just store all 100 versions individually in the repository?
What are submodules for with git?