Tree felling involves the complete removal of a tree down to ground level. The techniques used to fell a tree depend entirely upon the characteristics of each site.
Felling the entire tree in one go is occasionally possible but usually involves dismantling, i.e.: the careful cutting and lowering of sections to avoid damage to surrounding properties, structures, plants etc.
Occasionally mobile cranes are used to assist with dismantling which improves safety and is significantly more efficient.