Squat is where you have the barbell on your shoulders, you go down into a sitting position and stand back up. With better form than that, but you know what I mean.

For the bent-legged deadlift, the barbell starts on the floor. You start in a squatting position and grasp the barbell, usually with your hands outside your legs. You push through your legs and stand up; when you finish you're upright and holding the barbell in front of you at crotch level. Then you squat back down so the barbell is back on the ground.

...and it just occurred to me that you probably know that. In my experience, the way the legs work with the two exercises is more or less the same. It feels different starting from the squatting position instead of starting from upright, and, of course, the upper body is leaned differently, which makes the whole thing feel different. But in both exercises, when I'm pushing up, I'm mostly pushing through the heels and trying to drive the barbell upwards using the quads, hamstrings and glutes. I find that BLDLs hit my hammies and glutes more, while squats hit my quads more, but I've also heard people say the exact opposite.

Does that help answer your question?

I'm sure there are a bunch of YouTube videos of both exercises; I'm too lazy to find links. You might also want to search stumptuous.com.