Yes, there is. The -r option tells rm to be recursive, and remove the entire file hierarchy rooted at its arguments; in other words, if given a directory, it will remove all of its contents and then perform what is effectively an rmdir.
The other two options you should know are -i and -f. -i stands for interactive; it makes rm prompt you before deleting each and every file. -f stands for force; it goes ahead and deletes everything without asking. -i is safer, but -f is faster; only use it if you're absolutely sure you're deleting the right thing. You can specify these with -r or not; it's an independent setting.
And as usual, you can combine switches: rm -r -i is just rm -ri, and rm -r -f is rm -rf.
Also note that what you're learning applies to bash on every Unix OS: OS X, Linux, FreeBSD, etc. In fact, rm's syntax is the same in pretty much every shell on every Unix OS. OS X, under the hood, is really a BSD Unix system.