How plates move relative to each other determines the type of faults that occur at their respective boundaries. The above map (see Plate motion 'checkbox') shows the motion at various points on several plates in millimeters per year relative to the African Plate.
Trenches occur where plate boundaries converge. However, this does not mean the to plate are necessarily moving toward each other. The Pacific Plate (the world's largest) is responsible for the formation of the deepest trench in the world, the Mariana Trench.
The Mariana Trench (over 36,000 feet/11,000 meters deep) is at the convergence of the Pacific and Philippine plates. Yet both plate are moving in the SAME direction. The reason for the trench is their motion relative to each other. The Pacific Plate is moving twice as fast as the Philippine Plate thereby creating convergence leading to the formation of the trench.
Where plates diverge, ridges form. The largest ridge is the Mid-Atlantic Ridge where the North and South American plates diverge from the Eurasia and African plates. These plates are moving away from each other.
However, the Pacific-Antarctic Ridge is a location where the two plates (Pacific and Antarctic) are moving in the same general direction. The ridge forms due to the Pacific Plate motion that is around four times faster than the Antarctic plate. Relative to each other, these plates also diverge forming the ridge.