Answer

There is definitely a difference between the two. Many people confuse the terms, and some people who are really agnostics mistakenly give themselves the label of atheist.

An agnostic is someone who believes he, or people in general, can never come to know anything about ultimate spiritual matters. His refrain might be, "I don’t know if there is a God."

An atheist, on the other hand, denies emphatically that there is a God. The atheist’s refrain would be, "I know there is no God."