What is the meaning of h(r) in this protocol? Could somebody tell me what the meaning is of $h(r)$ in the protocol below?

‎‎$A‎\leftarrow‎{B}\quad:{h(r)‎‎}{,B}{,P{_A(r,B)}}‎
\\A‎\rightarrow‎{B}\quad:r$
As Ricky Demer already mentioned, $h$ is a hash function. 

In the realms of cryptography, it mostly points to a secure hash function. But in the end, it doesn’t matter if it’s a secure hash or not… $h$ is standard notation for “hash”.