A BarCamp Manchester is an event that is similar in many ways to a conference, but has several unique twists. The event usually has a series of sessions and panel discussions as well as plenty of opportunities to network. The one thing that separates a BarCamp from a typical conference is not the content, but the manner in which it's presented. All of the sessions, panels and other content at a BarCamp are provided by the attendees. You won't see "industry leaders" talking about technology that was interesting 8 months ago; you will be interacting with peers in your area and learning about things happening now.
At the event, there is a large schedule showing available rooms and timeslots. Anybody who wants to present can claim a timeslot. The event starts with a brief time for people to meet and post sessions, followed by presenters giving a brief summary of their topic.
For more information, check out barcamp.org.