As the name suggest, deformers deform the geometry of the object. There are a lot of deformers as you can see in the picture on the left, however I will only be explaining the Bend, Bulge, Twist and Explosion.
This bends an object.
You can also limit the amount of bend in an object by scaling the bend. I used a cylinder from the Primitives as an example because it is a better way of showing you.
This makes an object bulge or contract.
This twists the object around its Y-axis.
This explodes and object into multiple polygons.