A destructive plate boundary happens where an oceanic and continental plate move towards each other. The heavier, more dense oceanic plate is forced under the continental plate. As it sinks below the continental plate the oceanic plate melts due to friction in the subduction zone. The crust becomes molten called magma. This may be forced to the surface of the earth causing a volcanic eruption.
figure 1. Cross section of a destructive plate margin (source: Wikipedia)
The movement of the oceanic plate is not smooth. Due to friction the plate gets stuck. Pressure then builds up. The plate will eventually slip sometimes causing an earthquake.
The continental plate is crumpled by the pressure and forms fold mountains.
Destructive plate margins occur where an oceanic and continental plate move towards each other. Examples below include the Pacific Plate and Eurasian Plate and the Nazca Plate and the South American Plate.