The source material provides an extensive overview of the theory of plate tectonics, describing it as the dynamic movement of the Earth's lithospheric plates that drives geological activity. The core argument is that plate tectonics is the "unsung hero" behind Earth's habitability, establishing and maintaining conditions essential for life through several mechanisms. Specifically, the source explains how this process regulates the global climate via the carbon-silicate cycle and facilitates the cycling of critical nutrients such as phosphorus. Furthermore, plate tectonics is crucial because it creates diverse habitats for life and indirectly sustains Earth's protective magnetic field; finally, the text discusses how recognizing tectonic activity on exoplanets could narrow the search for extraterrestrial life.