What is an RPC?

[super6]

I've added a bitcoin module to my website so that people can checkout with bitcoin but it asks for a BitCoin RPC host address as well as a user name and password. I've google a bit and found API calls for RPC but no explanation of what it is and what this address should be, nor the login credentials.

[Stephen Gornick]

I've added a bitcoin module to my website so that people can checkout with bitcoin but it asks for a BitCoin RPC host address as well as a user name and password. I've google a bit and found API calls for RPC but no explanation of what it is and what this address should be, nor the login credentials.

To connect to the bitcoind running on the same host,
 you'll want to create or edit a bitcoin.conf and set rpcuser and rpcpassword:
 - http://en.bitcoin.it/wiki/Running_Bitcoin

[rollingpaperguy]

Where do I find the 'Host Address'? Is that my wallet address?

[kjj]

Where do I find the 'Host Address'? Is that my wallet address?

That is the IP address of the server running bitcoind.  If it is on the same server as the website, it is almost certainly 127.0.0.1 (or "localhost") instead of the actual IP.