When rocks are deposited normally, meaning there only are horizontal layers stacked on top of each other, we call them conformable. When there's an interruption, and something affects the deposition of rocks, this is called an unconformity.
There are three types of unconformities:
A disconformity is just an interruption in the layer between two other parallel layers. So, it's evident that erosion disrupted the deposition process a little bit, so that is called a disconformity.
An angular unconformity is the intersection between a rock layer which is at an angle, and a horizontal rock layer. In this picture, the bottom rocks are obviously tilted at a steep angle, while the rocks on top are deposited horizontally.
A nonconformity is basically a catch-all. It's when it isn't parallel between two layers, and it isn't strictly tilted at an angle.