Answer:
tectonic plates move in opposite direction
Tectonic plates are not necessarily moving in opposite directions, but if there directions are different they form plate boundaries. If they were moving in the same direction they would become the same plate. The more opposite the direction, the more obvious the fault.
Examples of plate boundaries:
Divergent: moving away from each other - mid-Atlantic ridge
Convergent: moving towards each other - the Himalayas (Indian plate subducting under the Eurasian plate forcing up the mountains)
Transform: sliding laterally along each other - San Andreas fault