Here's a breakdown:

* Oceanic plates are denser than the continental plates.

* Lithosphere-asthenosphere boundary: This is the boundary between the rigid, brittle lithosphere (which includes the crust and the uppermost mantle) and the hotter, more fluid asthenosphere (part of the upper mantle).

* Slab pull: As oceanic plates subduct (slide) beneath other plates at convergent boundaries, their denser material sinks into the asthenosphere. This sinking is driven by gravity, creating a pulling force on the rest of the plate. This force is known as slab pull.

Slab pull is a major driving force of plate tectonics, contributing significantly to the movement of tectonic plates across the Earth's surface.