Plate tectonics refers to the idea of Earth's outer layer being divided into a number of fragments or plates, all of which are in constant motion. These fragments or plates are known as tectonic plates and the Earth's crust is composed of such plates.
We can think of plate tectonics as a recurring cycle. To understand it, think about what happens at the plate boundaries. At converging boundaries, plates come towards each other, with one plate slipping underneath the other. At diverging boundaries, plates move away from each other. At transform boundaries, plates slide over each other. Thus, we can see that plate material is lost at some places, whereas at other places the new material is added onto the plates, thus bringing cyclic nature to this process and renewing the plates.
At a much larger time scale, on the order of 100's of millions of years, we can think about supercontinent cycling. It has been indicated that all the continents were a single massive continent known as Pangea, which broke up into a number of continents. Similar to this supercontinent, a number of other supercontinents have also been part of Earth's history (each spaced out by about half a billion years). And this supercontinent cycling causes periodicity in plate tectonics (breaking and formation of plates).
Thus, the plate tectonics can be thought off as a cyclic process.
Hope this helps.