What are stalls? Any tutorials?

Hello everybody, I’ve been hearing a lot about stalls lately, but I haven’t been able to find much on them, so what exactly are they? Can you give examples of 1a stalls? Many thanks in advance.

EDIT: I see… very interesting. How would you go about doing the first one Johnnie does (where he unrolls it from his palm)? Is there any place I can find tutorials for more 1a stalls (I’ve looked on youtube, but I only found a video that didn’t really explain)?

They are where the yoyo stops spinning without coming back all the way.
JD invented them: