'postbit' is the template that is used to display a single post. It will consist of all the elements need to display a single post (ie. poster information, post date, post text, etc..).
Hash like it is mostly used here at vb.org:
Is a 1-way encryption of data. You can encrypt it, but never decrypt it.
An example why this could be usefull. A plain text password gets hashed (encrypted) at the client side, and then sent to the server for verification. Server has stored the hashed value of the password and compairs it. Interception of the hash on any level could never be used to calculate the original value (ie the password)
See also:
http://en.wikipedia.org/wiki/Cryptog..._hash_function