A butt joint is made by placing the end of one piece of wood against the side of another and fastening them firmly to each other.
A butt joint is not very strong joint, but it can be reinforced in a number of ways.
Butt joints reinforced with biscuits
Butt joints reinforced with dowels
Butt joints reinforced with screws
Butt joints reinforced with spline
Butterfly joint
Pocket hole butt joints
Simple butt joints