CVS and Subversion Differences
In CVS, revision numbers are per file. CVS uses RCS (Revision Control System) as a backend, and each file has a corresponding RCS file in the repository. The repository is roughly laid out according to the structure of your project tree.
In Subversion, the repository looks like a single filesystem. Each commit results in an entirely new filesystem tree, so the repository can be likened to an array of trees. Revision 62 would refer to a particular tree - the way the filesystem looked after the 62nd commit.
In CVS, you may talk about 'revision 4 of source.c.' In Subversion, you would say 'source.c as it appears in revision 4.' In CVS, revisions 3 and 4 of source.c are always different. In Subversion, it's quite likely that source.c was not changed between revisions 3 and 4.
In Subversion, commits are atomic - they happen all at once or not at all. The whole change is applied (or rolled back) and is only visible to other users once completed.
In CVS, a commit alters each file in turn until it is done. This can lead to problems. For instance, if a network connect goes down in the middle of a commit, this can leave the CVS repository partially changed, and often unstable. If a user updates their working copy whilst another is committing a change, they may retrieve a partial commit from the CVS server.