If you’re making local commits (or local branch, or local merge, etc), you’re leveraging the distributed nature of Git. With SVN all these actions required being done on the server. This meant if you were offline and were thinking of making a risky change you might want to back out of, there was no way on SVN to make an offline commit which you could revert to if you wanted.
Of course if you’re working with others you will want a central Git server you all synchronize local changes with. GitHub is just one of many server options.
