Blower/Vac stands for a combination tool that is both a blower and a vacuum, but not at the same time. Most blower/vacs are designed to handle leaves in the fall. There are others that can blow general debris and pick up objects such as empty beer cans. Power of the machine will determine how effective will be the blowing action or the vacuuming action. One real benefit of the vacuum side of the machine is that in most cases the machine shreds leaves as it picks them up, usually with a 5 to 1 reduction ratio.
Most blower/vacs on the market are portables which you strap over your shoulder and direct with your hands on the handles. There are larger blower/vcs on wheels that you push around or are self-propelled.