Pagans believe in nature based spirituality. It may or may not include god(s) or godess(es). They venerate these beings, hoping to invoke their blessings.
Atheists know that the universe around us is spectacular enough that they don't need any supernatural beings to spice it up. They look at the Horse Head Nebula and realize it's so massive and far away that no god dreamed up by man could have created it.
Plus, atheists have a LOT more free time on their hands on Sunday mornings.
An atheist does not believe in any gods, the term pagan is a derogatory term coined by Christians to describe any European religion that is not Christian ( they used it as a blanket term for many different religions ).
The difference between an atheist and a pagan is that an atheist does not believe in any from of Devine Being or God. On the other hand, pagan believes in the Devine Being or God and have rituals to cerebrate different seasons and to honor their Deity.
Atheists do not believe in any form of god, deity or spiritual being. pagans worship the gods using strange and unethical ceremonies. Their religion and rituals revolve around nature. the term pagan was originated a long time. It was a term used by the Christians to refer to any person who was not christian. (a lot of them were connected to worshiping nature, but many also weren't and were just loosely grouped by the same term).