Florist Foam?

[ashley05]

I hope I put this in the right forum.

I have ordered seedlings from two different vendors: one paph and two catt alliance. Both times, they had florist foam on the roots. The paph just had a bit like it was supposed to be removed and someone missed a chunk, but the catts were sitting on a block of it.

So, now to my questions. What is the foam used for? Is this a common thing? Do I only need to watch seedlings only or is foam used with older plants?

Thanks!