They offer different types. You can pay top dollar for a refundable anytime ticket...or you can get one of the cheaper fares...if you read the details on thelower priced fares it will tell you what the terms are. If you buy a 'non-refunable' ticket, and they go on sale for less, you can cancel the original 'non-refunable' fare and get credts, but not a refund. The credits are valid for up to one year from the original date of purchase. I don't know if you had some kind of emergency, I think then you might be able to get a refund, or something like that, but you'd have to call them. It can be a little hairy cancelling a ticket, but it can be done. Also, in order to use the credits, you have to have the original confirmation number, so if you lose that, you might be out of luck. Southwest is having a fare sale now to Orlando. That is pretty much the lowest fare I think you'll find to Orlando.
Overall, I find their website to be MUCH better than any other airline's page. I just wish the other ones would wake up and smell the coffee. No wonder they are in economic trouble all the time.