Convergent Boundary
A convergent boundary is an area when 2 or more parts of the lithosphere crash together while moving. One of the plates (Usually the denser or older one.) bends and sinks right to the mantle. Don't forget with all the pressure friction and the plate sinking down to the mantle, earthquakes and volcanoes are common near these convergent boundaries.
http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/conbou.html
Oceanic-Continental Convergence
Oceanic-continental convergence is when an oceanic plate and a continental plate crash against each other. The oceanic plate falls under the continental plate. The place it falls down on is called the subduction zone. If a subduction zone is close to a oceanic-continental boundary, a trench will be created. A "trench" is under the ocean and is a deep part in the water.
Oceanic-Oceanic Convergence
Like what was said on "Convergent Boundary" when an oceanic plate crashes against another oceanic plate, the old, cold or denser one falls into the mantle. New crust is made and magma rises to make volcanoes.
http://www.passmyexams.co.uk/GCSE/physics/plate-tectonics.html
Continental-Continental Convergence
When 2 continental plates crash against each other they crumple up. Because of this, tall mountain ranges may form and earthquakes are possible to occur.