Verbs can take potential complements that indicate whether or not the action is actually possible. They are useful in Chinese to say if an action can take place.
Structure
Potential complements can be positive or negative. What this means is fairly intuitive - potential complements can be used to express that something can happen or that it can't.
verb+得/不+[complement]
Here the complement is the second part of the potential complement after 得 (positive) or 不 (negative)
Examples
我 听 不 懂。
Note that the potential complement and degree complement can sometimes appear to be the same; the difference can usually be seen from context.