Taken from Wikipedia:
The Unit is an American action-drama television series that focuses on a top-secret special forces team and their missions abroad, in addition to the effect their careers have on their home lives, wives and girlfriends
So it's still has the same background with 24, special forces team. But in 24, the main focus is Jack Bauer, not the rest of the team. Here's the difference.
Here's the front cover of the movie (remember David Palmer?):