Reinforcement is needed to prevent cracks and movement between the boards. There are a variety of different materials used to reinforce joints.
Paper joint tape is a thick piece of paper with small holes in it and has a crease along the middle for internal angles.
Self adhesive glass glass fibre mesh is a fibreglass tape that had glue attached to it, It is strong, easily cut and has an open mesh.
Reinforced paper corner tape is used for external angles. It has two thin metal strips on one side of the paper.
Drywall metal beads are just metal beads that are used for reinforcing external angles. The beads are more expensive than reinforced tape but are easier to use on external angles.