You don't "need" a desktop environment. A DE is just a bundle of software made to work nicely with each other; typically window manager, taskbar, launcher, file manager, terminal emulator, plus a bunch of other stuff. If you really want you can pick bits and bobs from different DEs, or not from any specific DE, and build your own thing, the way you want.

That said you still probably "want" a DE though. At least, at the start; it simplifies things by a lot.