What is it called when a batter warms up before the pitch is thrown? (pitching, stance)

[compwiz02]

While the pitcher communicates with the catcher, usually the batter warms up with his bat and does some movements with the bat before going into his final stance. what is it called and why do batters do that? lately, I haven't seen them do that. they go to the batter's box and go right to their stance and wait for the pitch.

[Hemlock140]

When a player is next to be up, they are in the "on deck" circle. Usually they will stick a weight onto their bat and swing it around, which then makes the bat seem lighter when they are at the plate. Baseball is a sport with many superstitions. What the player does one getting to the plate may be what they did the last time they hit a home run, so they think it will bring luck. On the other hand, if they struck out last time, they may avoid what they did then. Some may even make moves meant to distract and annoy the pitcher, Ichiro was a good example, the way he stuck his bat straight out.

See: https://fansided.com/files/2013/07/7409252.jpg

[Joe the Photog]

I believe the OP meant when he is already in the batter's box, but before the pitcher goes into his pitching motion. I don't know what it is called though, if anything.