Divergent plate boundaries separate from each other, or spread apart. This is caused by tension between the plates.
When Oceanic plates separate, mid ocean ridges and volcanoes may be formed, while earthquakes may occur. Examples of these are the Mid-Atlantic Ridge and the East Pacific Ridge.
When continental plates separate, usually rifts or volcanoes are formed in the process, and example of these are Mt. Kilimanjaro and the East African Rift
Convergent Plate Boundaries slide towards each other due to compression. This usually causes the creations of deep ocean trenches and volcanic arcs (oceanic plate to continental plate) or mountains (continental to continental plates)