Here's a breakdown:

* Plate tectonics is the theory that Earth's outer layer (the lithosphere) is made up of large plates that move and interact with each other. These plates are constantly in motion, driven by convection currents in the Earth's mantle.

* Convection currents are created by heat from the Earth's core. Hotter, less dense material rises, while cooler, denser material sinks. This creates a circular motion that drags the plates along with it.

* Seafloor spreading occurs at mid-ocean ridges, where new oceanic crust is created as magma rises from the mantle and cools. This new crust pushes older crust away from the ridge, creating a spreading effect.

* Continental drift is the movement of continents across the Earth's surface. This movement is driven by the interaction of plates at their boundaries.

In short, plate tectonics, driven by convection currents in the Earth's mantle, is the primary force behind seafloor spreading and continental drift.