The participants, working in small teams, are attempting to build a complete video game in under essentially a day's worth of time. Once the time allowed has elapsed they will share their creations with the crowd for review.
Talking with the event organizers, the game jam is not a competition - there are no prizes. The purpose for the event is to allow people to join groups of other game developers, designers, artists, and enthusiasts and spend a weekend building a game. Of course they are not just building games, they are making new friends, industry contacts, and learning many of the crucial skills it takes to work in the team oriented environment that is modern video game development.
It's great to see an event like this happening in St John's - I can't wait to see some of the results of the games, and to see if this will become an annual event for the local game development community.