I don't mind or I don't care?

which one WHAT is the difference?

"I don't mind" means you are mentally happy / agreeable either way. It does not matter either way.

"I don't care" can mean the same thing as "I don't mind", but depending on context or attitude, "I don't care" CAN be rude/unfriendly. It really depends upon attitude and the way it is expressed vocally. Text alone cannot express true feelings/motives for the phrase.

Example: When I ask my wife if she wants to eat mexican food tonight and she replies "I don't care" I may have to reconsider where to eat. She might just mean she is not hungry and it does not matter, or that she will go, even though she doesn't really want to. Expression (the manner in which the phrase is spoken) is very important.

If I ask her and she replies "I don't mind", we usually go out to eat mexican food. I hope this helps!