What's the main difference between a "mole" and a "birthmark?"

Native speaker’s answer
Rebecca
The main difference between a "mole" and a "birthmark" is that one gets a birthmark right after being born, and "moles" could form at any point in time and are usually smaller and more circular than birthmarks. Ex: I have a couple more moles on my face since I was in the sun too long this summer. Ex: I have a birthmark shaped like Australia.