According to http://www.thefreedictionary.com/ collaboration means to work together, especially in a joint intellectual effort.  It used to be the only way this took place was face to face.  Teachers have voiced their opinion that collaboration is the most effective form of professional development because the strategies they learn have already been tried in an environment similar to theirs.  They are not learning about strategies being used in New York and their effectiveness and then expecting to have the same results on their kids in Georgia. This is across the hall or next door information that has already been tested for effectiveness on children similiar to what is actually in their classroom.  \

Collaboration has evolved to the point where there are numerous ways to do this on the internet.  One website that I posted to listed 15 different sites to collaborate online (www.missiontolearn.com/2009/08free-online-collaboration).  Another educator also created a blog about online collaboration and how important it is (http://www.teachweb2.blogspot.com/).