How/where do I publish a poem online?

When I publish a poem in a magazine what rights do i give up?

• I want to send a poem in to a few magazines. Do I still have the right to publish it again else were (like in a book) in the future?

• Answer:

  What does it say in the submission guidelines? I have heard for short stories it is the mag can use it for a period of several months like six months or a year