Do you know what species it is? Some from Guatemala, the really huge multi-branching kinds are like trees but very cold tender and rot from the inside out. This kind has stiff, waxy leaves about 60cm long x 7cm wide and can grow up to 10m tall. There are three or for variegated forms, mostly derived from Dutch green-house growers, even those sold in Australia. The nurseries like these because they are dead easy to propagate in a heated European greenhouse. The big branches can be cut up onto short sectiosn and rooted standing up, thus making tall indoor plants for northern Europe. The trunk sections van also be split in half vertically and rooted lying down on potting mix. This produced heaps of smaller plants that can be potted on and sold quickly.
There are other Yuccas from the SW USA that must be grown from seed, a much slower business, and the seeds harder to get and expensive too. This region is where the cold hardy Yuccas come from; the ones that withstand snow and blizzards every year. As a general indicator these Yuccas have very narrow silver leaves. Some make trunks (the Joshua Tree) and some do not. All are lovely but tend to grow slowly whereas the Tropical ones are much faster.