asm stack related registers

i have a few questions about the stack registers esp and ebp.
what does this do? why are we moving the stack pointer into the stack base pointer?

This often happens at the beginning of a stdcall function. As you know arguments are pushed to the stack before a call is made. When the function is then called and the stack pointer is moved into the base pointer the functions sees the stack as if it hasn't been used yet. Because for as far as the function can see, the stack begins where it ended for the caller.

This is often how stdcall functions are compiled:

Since the ebp register normally remains unused by the function the stack pointer can be moved back when the function is done executing. This way the function removes all but 4 bytes from the stack, the return statement (ret) removes even this (it's the return address) Now it is as though nothing has used the stack from the callers perspective, all is as it was before the call.

I hope this answers your question, but you should keep in mind that this is the Cpp section, you can also post your question in the asm forum and vm/pm someone to look at it.