Cascadia is a geographical region. It includes Oregon, Washington , and BC west of and including the Cascade Mts. I use it as opposed to Pacific Northwest because a) I find it a more evocative term, b) it is more accurate to the content than PNW would be, and c) I have a sense that the term will become more widely recognized soon, due to the popularity of the region and a lot of activism/movements/politics that are centered around this concept and use the term.