What is an SAE / SASE / Stamped Addressed Envelope?
When submitting to magazines, agents, and publishers by post they will often require you to provide them with a means of replying to you at your cost (and without them having to even write your name and address out!). They will therefore request you include an envelope with your submission, which should be big enough, and have attached to it sufficient postage, for the return of your submission, or reply, as required. As well as attaching the postage to the envelope, you should also write your name and address on it.
This is commonly referred to as a stamped addressed envelope; SAE; self-addressed stamped envelope; or SASE.
If you are submitting overseas, remember that postage from your own country will not be accepted, and you may need to provide an International Reply Coupon.