At the top right corner of the screen, you can see a minimap. This shows your surrounding area, players and mobs nearby, and much more.
Hit B to create a waypoint. You can give it a name and a color. You can see this waypoint in the world and the minimap where you placed it.
You can hit Control+J to toggle the minimap.

If you hit J you open the map. Here you can see all the places you've ever been to from a bird's eye view, as well as any waypoints you've placed.

The bottom left button in the map opens the waypoint management menu.