What’s the difference between the terms "affordances" and "signifiers"?

I do not understand the difference between the concepts affordances and signifiers. I am given the following definitions:

Affordances: "Relationship between properties of an object and the capabilities of an agent that provide clues to the use of an object. Affordances must be perceivable / visible to be effective"

Signifiers: “Any mark or sound, any perceivable indicator that communicates appropriate behavior to a person”

Could someone explain with examples? Is it that signifiers signal how an object can be used and affordances is how it actually can be used? Rereading that last sentence I realize it made no sense, what I meant is do signifiers convey how an object is supposed to be used and accordance is more of a matter of reality in how it can be used.