I actually started writing an article on this, but it's been sidetracked with travel and other stuff. However I do mean to get back to it at some point.
In the meantime, Jamie Thomson went ahead and wrote a nice entry on Business Intelligence, what is it and what is it not?. Jamie does a good job of breaking up some myths and then giving a short explanation of what it means from the practical world of someone working on it daily. Highly recommended.
Steve Jones is the editor of SQLServerCentral.com and visits a wide variety of data related topics in his daily editorial. Steve has spent years working as a DBA and general purpose Windows administrator, primarily working with SQL Server since it was ported from Sybase in 1990. You can follow Steve on Twitter at twitter.com/way0utwest