The interface is very user friendly, the only thing that a new user to editing will notice is the 4 windows in the view. They each represent a view from a different angle. The 3D view gives the editor a view of how the level will look when run in Quake, obviously it is in a wire-frame form, but it is clear to see how this represents the view within the actual game.
Buttons from left to right:
Creates new map file template.
Loads map file.
Saves open map file.
Cuts selected parts of map.
Copies selected brushes or Entities.
Paste's selected Brush or Entity.
High light's selected object.
Move's selected object.
Rotates selected object.
Scale's selected object.
Vertex move allows a corner of a brush to be moved.
Edge move allows a single edge of a brush to be moved.
Face move allows a single face of most brushes to be moved.
Move eye allows user to move map around in viewpoint, vertically or horizontally.
Rotate eye allows user to view map from different angles, by rotating different viewpoint to different angles.
Zoom eye lets user zoom in and out, the different viewpoints.
Add object lets user add differert shapped brushes, entities and prefab's.
Delete object, lets user delete selected brush or entity.
Scope Up / Scope Down
Scope up /Scope down, is used as grouping brushes and entities together.
Render lets user select what type of 3D view they want, ie. textured, wireframe etc.
Snap allows the user to select the size of the minimum measurement allowed.
Tex lock, locks the textures of the brushes.