Tectonic plates can slide against each other, move together or move apart. When plates slide along each other, you get what is called a slip-strike fault, and earthquakes. When plates move together, one of the plates must sink, which is called subduction. Subduction causes mountains to form, as well as earthquakes and eruptions. When tectonic plates move away from each other, the earths crust cracks and magma fills the cracks forming a ridge. This is also accompanied by volcanoes and earthquakes.
When tectonic plates move together and rub against one another, this can cause extreme vibrations that later cause an earthquake. The earthquake can cause terrible rock slides, buildings will fall down, electricity will go out, and many more severe problems.