It's hard to tell a scam from a non-scam sometimes. But a scam often goes like this: You get sent an email or a letter (or maybe you respond to an advert) asking you for some poems. You send some and you get a letter back saying some poetry organisation in America or somewhere loves them and that you have been specially selected to appear in their prestigious publication. They don't offer to pay you for this. In fact they say you can get a special price on the resulting publication. You also get an invite to a big convention or prize giving but they don't offer to pay you or put you up, but they do emphasise the size of the plaque or trophy (which you may or may not have to contribute to financially). You get very excited by this - and that's fine if you know what it is and you're happy with this arrangement.There are other set-ups which are cooperative and might involve you paying (but they're upfront about this and tell you). You decide if you want to be involved in them on their merits. Some local projects (for example) are like this.
There is also what is called 'partnership publishing'. This involves the writer paying something upfront to assist with printing/distribution. There have been considerable developments in this area. Random House with Ex Libris and Amazon's Booksurge now have imprints which have this sort of this arrangement.
Then there's 'vanity publishing' which is a sub species of 'self-publishing'.
Vanity publishing is where a writer goes through a printer or a press and pays for everything but sets it up as so that it appears that they have been published by standard publisher.
Self-publishing is the author publishing their own work and being open about it. This often happens when the runs might be small, apply to a niche market, or be the special passion of the writer. Family histories etc are often self-published. Some self-published books have gone on to great success. It's rare though. There are a few links about self-publishing on the Rejections page.
What I'm calling 'standard publishing' is where the publisher pays the printer, arranges distribution, advertising and pays the author royalties (ie a percentage of the retail or other price).
