This is when the two boundaries push together and form fold mountains to form a the Hymilayers etc. The boundaries push together and raise as neither will fall under each other.
Distrcutive plate boundaries
The distructive plate boundaries are the boundaries in which one of the plates falls underneathe the other boundaries. This is usually the oceanic plate as it is heavier and falls underneathe.
Concervative Plate Boundaries are the plate boundaries in which the two plates are pulling apart from each other and a volcano or other magma souce fills the middle with new land. The land is created.