Intros are the main thing that the motion design community makes. It is what the community revolves around and is what most designers make.
An intro is an 5-20-second introduction made for YouTube channels to introduce the viewer to their channel. Most intros contain the text of the channel in a 3D or 2D form, and usually has background music. The intro is most of the time synced to the music with screen pumps at each beat. Intros have smoke and particles in the background that move around with the text. Different effects and styles are what make each intro unique and different from each other.