pink line?

what is the pink line? what is the use of it?

If you mean the vertical pink line in the timeline, that’s the scrub bar. It indicates which frame is currently showing. It will automatically move when playing the animation, or you can move to a specific frame by clicking on a frame in the top part of the timeline, where the frame numbers are, or by dragging the top of the scrub bar.

i put it a litle small one time. is that like a limit?