If the individual items in your shipment are light enough for you to remove from the truck, you do not need a lift-gate. If your item is over 120 lbs and you live in a residential location (or do not have a loading dock), you will need a lift-gate.
A lift-gate is basically a hydraulic lift used to raise and lower items from ground level to the level of a delivery truck or trailer. Most freight companies deliver items on a truck which are usually designed to load and unload at a loading dock or with a fork-lift. If your delivery location (ie, residence) does not have a loading dock or fork-lift and the item is too heavy to remove from the trailer by hand, then you would need a lift-gate.