Overhear or Eavesdropping?

What's the difference between "overhear" and "eavesdrop"?

They both mean that you hear someone's conversation without their knowledge.

• Overhear - You're not trying to listen, but you still hear the person talking.

"I overheard him on the phone yesterday."

• Eavesdrop - You are trying to listen and hear what the other person, or people are saying

"Were you eavesdropping?"