There are countless woodworking joints and modified joints that have been developed to to fill the need of simply joining two pieces of wood together.
Every woodworking niche has it's own favorite joints that work best for it's applications. For example, the construction industry uses the butt joint as a standard, the cabinet industry likes the pocket hole joint or the dowel joint and wooden boats are built with scarf joints and the tongue and groove joint.
From the need to adapt certain joints to special applications or faster production these standard joints have been modified and sometimes new joints are developed such as the pocket hole joint or the biscuit joint.
Some joints are used not only for their strength but also for their aesthetic appeal. The dovetail joint and the box joint are used just this way in the cabinet and furniture industry. They're pointed out as a sign of strength and quality craftsmanship.
Basically joints are developed to solve a particular problem or adapt to a certain
application. These joints become the standard for that application until a new idea comes along. Then another new joint is developed!
You could say that some joints, by themselves, have become a art form, a industry, and sometimes a subject of great dilemma.
Since the first carpenter created the first joint people have been modifying and
inventing new types of joints. Even today as a standard joint gets a modified upgrade, a new joint is created and it then becomes the new standard.
Although joint design seems to be endless, I'm listing some of the most
common woodworking joints along with their common uses.
Mortise and Tenon Joints
Pocket Hole Joints
Tongue and Groove Joints