Each continent is embedded onto plates, which are made from lithospheres - Earth's outermost layer. Because this layer is stronger than the underlying layer, it is able to move. Several forces encourage it to do this, which means Earth's landmass remains the same, but the location of continents shifts slightly each year.
The plate tectonics theory first developed in the 1960s and 1970s as a means of explaining why Earth's continents have moved throughout history. It states that the layer underpinning the continents, the lithosphere, is able to move. This occurs when the seafloor's motion creates drag, and when it generates a downward suction. Another theory is that the sun and the moon generate tidal forces that encourage it to move.
The movement from plate tectonics is fairly minimal, at a rate of 0 to 100mm per year. The lithospheres are made of seven primary areas, as well as some minor regions. Sometimes the plates are able to move past each other, but at other times they crash, giving rise to events like earthquakes. In addition, crashing plates can cause volcanic eruptions and the development of mountains. While it is not always dangerous to live on or near a plate boundary, some areas do experience more earthquakes as a result.