Deism: belief in God.
Atheism: no belief in God.
That is the difference between deism and atheism.
As for deism vs. theism, God created the universe, the laws of nature that govern it, and set everything in motion. There is no need for a hands on approach. God also created living beings with free will. We make our own choices and take the consequences, good or bad, that come with those choices. Where a theist believes that God intervenes, they are stumped when asked "why do bad things happen to good people"? Their usual answer is something along the lines of "its God's will, we can't see the bigger picture, everything happens for a reason, etc." Those are all rehearsed, cop out answers because they can't explain it. If God controls everything as many theists believe, then God is at fault for every murder, rape, theft, natural disaster, terrorist act, etc. It is at this point that the theist will try and put a spin on it to take the blame off of God. They want it both ways...God is in charge, but only for the good stuff. The devil causes the bad stuff to happen! Of course, the moment they go down this road, they are saying that God is NOT in control and that the devil has power to do whatever he wants, outside of God's authority. Thus the web gets bigger and deeper. Sigh.
A deist can easily explain that same question with free will. "Why do bad things happen to good people? Because someone chose to do something bad, plain and simple." We are responsible for our actions. That is the logic of deism. We typically do not believe in supernatural boogiemen (devil, demons, etc.), and view God as an omnipotent being that is not bound by any law, doctrine or system of belief. God is God, and answers to no one. He is transcendent. As the creator, if there was a devil or demons, He could simply snap His divine fingers and un-create them.
Every single document ever written about God, regardless of religion, was written by the hands of humans and includes their biases, preconceived notions, superstitions, cultural beliefs, and mythologies. They can claim divine inspiration all they want to, but they can't prove divine inspiration. Deism is a simplistic, logical approach to the belief in God without all the man made drivel that is recorded in "holy books."
Deism also has no problem with science. We encourage scientific discovery and advancement. God gave us intelligence and we SHOULD be using it. We are not stuck in the Stone Age, Bronze Age, or Dark Age (yet people cling to beliefs from those ages). We lost over 700 years of scientific advancement during the Dark Ages because of the Church and its persecution of science. Imagine where we would be today had that not happened! 700 years into the future...