You can trigger a cutscene for someone from script or manually using the command :
*cutscene [PLAYERNAME] [CUTSCENE_FILENAME]
The cutscene is contained within a file on the server that the client will download. Cutscenes allow you to control the camera and player, add models and graphics, add UI text and do things like play music and control special effects.
e.g. You might have a cutscene triggered when a new player joins, that pans the camera around to show them their environment, and tells them some stuff about your world. Or you might have a building (or item) that when accessed triggers a cutscene giving the user a storyline or clues that leads to bigger things.
Cutscenes use a different language (don't ask), where you set thing such as 'the camera will pan from this point, to this point, from time x to time y' or 'this model will move from here to here and do this animation'.
If you're new to world building, come back here later - you'll get more benefit exploring the event scripting side of things. If you're an advanced world-builder, appropriate use of well-crafted cutscenes can make a huge difference to the appearance of your world.