diffs plural, not diff singular, because not everyone agrees 1. on what the differences are or 2. that there are major differences. i don't lose any sleep over it.

g

There are easy definitions that are widely accepted yet many people are confused.

Atheist: Lacks belief in any deities. NOTE: not the same as disbelieving, although calling it disbelief is a common semantic shortcut.

Agnostic: Lacks knowledge of any deities. NOTE: correctly speaking -- does not believe one CAN know anything about deities because they are inherently non-falsifiable.

The difference is that one describes the belief position about gods, the other, the knowledge position. They influence each other but can vary independently.

If you think gods are non-falsifiable then it's pretty hard to afford belief to them, and if you lack any god beliefs it's hard to stake a knowledge claim. So these are really just two side of the same coin.

It's easy:

Atheist (me): a person who does not believe in any gods.

Agnostic: doubts the existence of a god. A person who holds neither of two opposing positions on a topic.

"I don't believe in an invisible being that resides somewhere beyond the clouds," I say cheerfully to Christians who try to convert me.

Of course, it doesn't work. They always try to pin me.

"Can you see the wind?" a Christian zealot recently asked. "How do you know the wind exists if you can't see it?"

"Wind is scientifically proven and explained," I replied. "An invisible god is not."

I don't think so, but I don't know for sure.

Yes, more times than you want to know. The problem here is that when you state 100 percent that there is no god you have shifted the burden of proof to yourself and you must show evidence. There is no evidence either way.