A flange is used on all modern toilets. It is a fixture that has a rim that is attached to a pipe which in turn is connected to the drainline. A flange has bolt holes spaced to accomodate tee bolts which are used to bolt the toilet down. You put a sealing ring, either wax or the newer waxless, on a horn that is located on the bottom of the toilet and this horn with the ring fit into the flange. The sealing ring seals the water from the toilet and the sewer gases from the drain out of the house. The flange in most cases makes a straight down connection with the drain and are non adjustable. The offset flanges are capable of swiveling so that you can adjust plus or minus a couple of inches to accomodate a toilet that has more or less than the standard 12" rough in. Your main problem will be in removing the old flange so you can attach the new one. I would suggest you have a plumber do this. It isn't rocket science, but removing the old flange without damaging the drainline can be trickey. This would also assure that your toilet is installed correctly,