You try to capture the essence, flow and rhythym of the pose without going into details. I have known this method for a long time, but only recently, I started to regularly make gesture drawings. And this really helps a lot, as you learn to quickly see the form and flow.
Here and here are links to some gesture drawing tools, which change pictures after a set amount of time.
I mostly use the second one as it also has models without skin (only 3D models, no humans were harmed in making them), so you can use it for anatomy observations as well. And it has camera angles that wouldn´t be so easy to do with a real model.
The first link has photos of real people also with clothes, which is a different sort of gesture drawing, because the clothes sometimes change the form.
Here are some examples from the last 2 weeks (there are also some studies that took longer...and some doodles):
|Gestures and some studies|
As you can see, the drawings do not have to be perfectly beautiful pictures with perfect proportions and rendering etc., the main goal is to get a feel for poses and the flow of the human body in motion.
I try to do a couple of these gestures every day, because they are fast to do and you learn a lot. I can highly recommend this to anyone, who wants to learn how to draw the human figure.