Scrum: What, Why?
Just read this amazing article on Nettuts+, about SCRUM. For a time I have been writing something similar, and when I was it on Nettuts+, just thought why not just post a link, as this one is much better than mine will ever be!
To summarize, in my views and experience: SCRUM is a software development methodology for managing projects and/or software development. As the SCRUM employs the method of small iterations instead of long development cycle. In each iteration developers get to work for a time, where they will develop new functionality defined in tasks chosen and prioritized by the assignment giver.
At the end of each mini cycle the development team demos what they have done in the iteration. This enables teams to fix any bugs in an early state.
This was what I had written so far, for more check out: SCRUM: The Story of an Agile Team