Originally Posted by genejockey

Almost nothing. No peer review. A poster is literally that - you make a poster with your methods, results, and conclusions and physically stand by it to present it during a session where there are dozens to hundreds of other posters (depending on the size of the conference) to answer questions from attendees. Conferences often put together a book with all the abstracts, so you can choose which posters you want to visit, based on your own interests. The abstracts are often then published on the conference's websites.

Abstracts are generally not peer reviewed in any way because they don't contain the data, and posters don't carry the weight of an actual published article.

This is something we in the Scientific community understand, but lay people do not - the appearance of an assertion in an abstract is damn near meaningless.