You need to carefully review the contract yourself and become contract savvy. A contract lists the terms of agreement between you and a publication when a piece is accepted by the publication. There are several parts to a contract. It is vital you read all of them carefully before agreeing to it, since once the contract is signed there is no going back and changing your mind. In some cases, you might be able to discuss your contract and make changes at a later date, but DO NOT count on it.
All publications are different.
Some publications want to buy ALL rights or just one times. To review what the different rights are, please view my part two series on rights on this site. There are different contracts for different types of publication. In next week's article. I will discuss more on contracts and the different ways you can be paid for your work.