A commune is a group living situation where people share everything. Communes were popular with the peace-loving hippies of the 1960s.
In Europe, a commune is a small administrative district. But in America, it's a way of life. A bunch of people with similar beliefs might all decide to get a big house and live communally, sharing the cooking, bills, and everything else. You can also commune with something, like nature: that means to be in tune with nature and very receptive to it. To commune can also mean to receive the Catholic communion.