Cabinet joinery can take on many forms. When considering the frame many options exist,
some more rigid than others, some faster and some more elegant. All depending on
who is making it, whether or not cost is the greatest factor, ease of production,
etc will all sort of dictate what is used.

The cheapest, fastest, and easiest would be a pocket screw. Cabinets and furniture
assembled together as such would tend to be cheaper and quicker. So if cost is the
deciding factor, than this is probably what you'll get. It will hold together well
enough, but even with glue, end grain doesn't really hold well when glued, so the
glue won't be doing much to keep the joint together. All the structure of the joint
is in the screw.
The next would be dowels. Holes are drilled on either side of the joint to allow
dowels to be glued together.
In this case, you're relying on
the dowels to "bridge" the joint and hold the two
sides together with glue. Glue joints tend to be stronger the the wood it's holding
together. If you were to glue two pieces of wood together and pull them apart until
they failed, chances are that the wood would split before the glue joint failed,
meaning that the glue is inherently stronger than the wood itself. However, in this
case, though somewhat preferable to the pocket screw, the dowel is the weak link
in the chain. But it is the quickest of the glue joint method.
Mortise and tenon is by far the strongest and more durable of the connections. It
starts by cutting a tenon in one of the boards. This is stronger than the dowel method
in that you're relying on the board itself to tie into the other. You cut a corresponding
"hole", or mortise in the other board to slide the tenon into. For millennia artisans
have used the mortise and tenon joint from furniture making to barn building to create
solid connections. Before the advent of modern wood glue tenons would be fastened
to mortises by way of a dowel drilled through the mortised board and tenon. With
the use of glue in place of the dowel, the joints become as permanent as a single
board.
Here is a desk built by Matthews Custom Construction using only mortise and tenon
joints. No metal fasteners were used in it's construction.

If you would like to see how to cut tenons on a table saw, watch our video. The link
is provided.
http://youtu.be/42ErjJYE_L0
Kitchen and Bathroom Remodel Riverside, Ca