Separated means a couple who have decided not to live together but are still married according to the law.Maybe they will get divorced or maybe they will make up and get back together again.Divorced means that they have already officially broken up their marriage by signing some paper and going through some legal process to stop being married.I hope this helps.

In the United States, the laws of marriage and divorce are state law and different in every state. However, there is usually a difference between "a divorce" and "a legal separation." A legal separation is not a divorce. The partners are still married. They are living apart, their finances become more independent, but they cannot re-marry.

One reason for legal separations are that at some times and places and in some situations it is less difficult and less adversarial than a divorce. It can also be a sort of trial period during which the couple decides whether or not they might be able to reconcile.

Seperated may also imply a tough time is occuring in the marriage and the two have basically made an agreement to allow each other space and the freedom to have a romantic encounter outside of the marriage. Divorced means that the two have made a legal agreement to end their marriage. 

I think Ruthi's answer is very good, but I wanted to add something - it's up to the individual person who calls themself "separated" whether they are single or not.  Some people separate in hopes of getting back together, but some people separate while they're waiting for their divorce papers to go through.  A person who is technically only separated but knows they are getting divorced may consider themself single, and may go out and date new people although they are still legally married.

Thanks Dwane M.