Something described as being 'up for grabs' is available and ready to be won, claimed or taken. This expression is often used to talk about prizes. This is an informal expression best suited to casual situations.

1. I can't resist buying a lotto ticket for tomorrow night's draw. There's £10 million up for grabs!

1. Now that John has retired, his position is up for grabs. I think I might put my name forward for it.
2. The boss's financial difficulties means that the whole company could be up for grabs if the right offer comes along.