You can wear it or wield it. A Prop Replica either adorns your clothing , is clothing like the character of the movie or TV series, or can be wielded in hand. This doesn't generally mean they were used in the show or movie production just that its an authorized release for all the associated fun.
Can I pre-order Prop Replica items?
Yes, in fact its the biggest area where you should consider doing so. Prop Replica items, unlike action figures, are actually expensive to produce. With Action Figures, even great ones, most of the cost is in the licensing. In practical terms if something is a "hit" they can make more of them. With Prop Replica's that are authorized the actual cost of production is much higher for the major manufacturers they have to have exact specification get the factory to re-tool to make them and oversee production. The runs tend to be run and often once its gone you won't see the item again , even the most popular hits for a year or two.