There are a few different geological features that occur when tectonic plates interact.

First, the plates could be moving apart from one another ("a diverging boundary"). This can lead to valleys called "rift valleys." One famous example is the East African Rift Valley Photos and more info at african rift valley Kenya.

Diverging plates are also the cause of mid-ocean ridges. Mid-ocean ridges occur when plates move apart, and magma comes up and fills the gap between them. When the magma cools, it becomes an underwater mountain system at the boundary where the plates move apart.

Another way tectonic plates can interact: they can collide! This is called a "convergent boundary." When the plates move together (converge), the denser plate will be forced under the less dense plate (this process is called "subduction"). When the dense plate is subducted, it will eventually melt. Convergent boundaries between oceanic plates can lead to deep-sea trenches (including the Mariana Trench- the deepest part of the ocean!). When oceanic plates are subducted under continental plates, we get mountain ranges (and usually volcanoes) at the edge of the continent. It can also happen that two continental plates converge and form mountain ranges: this is how the Himalayas formed! Here is some more info about how tectonic plates made the world's tallest mountains: Himalayas.

Finally, tectonic plates can interact by sliding past one another. This is called a "transform boundary." For example, one plate could be moving North while the plate next to it is moving South. As the plates grind past one another, they can cause earthquakes. The San Andreas fault is an example of a transform boundary. There is information and a video at San Andreas Fault.