Tom sees a fire. He runs up to see the fire. A fireman yells at Tom, "Hey, you! GET BACK! Don't come so close to the fire. You can get hurt!" ***** Tom: I came to this city a year ago. I hate it. Mona: Well, if you don't like my city, GO BACK to where you used to live. ***** Mona: I really liked my dinner at your restaurant. Server (waiter or waitress): We are so glad that you decided to dine here. Please COME BACK very soon. Mona: I plan to come back tomorrow. I love your food!

"Back" in this context can mean 2 things. It can mean "away (from something)," which is more of a spatial meaning. Or it can mean "where you were before," which is more of a temporal meaning "Come back" could mean "come away (from something)," or "return (to somewhere)." "Go back" often means "return" as well, but it can also just literally mean "move backwards." Fun Fact: When flipping through a book, if someone is flipping through it from the end to the beginning, and someone says "go back," it is ambiguous whether you should go back in page order, or return to where you were before (forward in page order). "Get back" usually just means "move away (from something)," When talking just about physical location, it is pretty much just like "go back." But, there are a lot of metaphorical uses for it, like this: http://www.youtube.com/watch?v=IoMi8aWLDCs

Get Back (get even, settle, winback) 1. Recover something or somebody that appeared to be lost "We got back the money after we threatened to sue the company"; "He got back his son from the kidnappers" 2. Take revenge or even out a score "I cannot accept the defeat--I want to get back" 3. Get one's revenge for a wrong or an injury "I finally got back with my old enemy" Go Back (recover, recuperate, recur) 1. Belong to an earlier time "This story goes back 200 years" 2. Return in thought or speech to something 3. Regain a former condition after a financial loss "We expect the stocks to go back to $2.90" Come Back (counter, recall, rejoin, repay, replication, retort, return, riposte) 1. Be restored "Her old vigor came back" 2. Go back to something earlier "This comes back to a previous remark of his" 3. Even the score, in sports 4. Respond in a quick, clever or humorous way AS A NOUN: Comeback 1. A quick reply to a question or remark (especially a witty or critical one) "it brought a sharp comeback from the teacher" 2. Return by a celebrity to some previously successful activity