The straight answer to your question is; ask your HR Rep, he is supposed to tell you.
But chances are that noone will tell you.
You have to come up with your own enterpretation of things.
For some; it could mean something that could be taken away from you at some point in time, if conditions change during your contract or after renewal.
For others it could mean just an internal accounting trick.
For you, it could mean, take it when it's given; and when it's taken away from you, then decide if you stay or pack your bags.