Surface

Surface is the side of a brick. It can be 6 kinds.

Stud
Main Article: Stud

Studs relate most to the connectors on LEGO bricks. They appear to be bumpy, but are 2D.

Inlet
Main Article: Inlet

Inlets are relate to the bottom of a LEGO brick. Inlets will only connect to studs and weld.

Weld
Main Article: Weld

Weld is the strongest, and will hold anything. They appear as Xs on the part.

Glue
Main Article: Glue

Glue is the second strongest, and can only hold a ball though.

Universal
Main Article: Universal

Universal is a combination of stud and inlet. It will connect to inlet and stud.

Hinge
Hinge

Hinge is a non automatic motor. It will only spin by gravity. It is the thing used to connect wheels to VehicleSeats.

Motor
Main Article: Motor

Motor is automatic, if put on Constant. If you connect another brick, it will spin if unanchored.