Commerce is the means by which members of the community interact economically. When building or running a community it is not likely that you would have to actively promote commerce but it is important to be aware that commercial interactivity is a basic element of community and should be a consideration as various decisions are made regarding other aspects of community. In a physical community it may be helpful to have areas where commerce is a central activity.
Commerce generally involves financial transactions, but it can include non-financial transactions as well.