Ok, I have extremely limited knowledge in dentistry. I do know that root canal procedures get rid of the nerve tissue inside of the tooth and replaces it with some sort of bonding substance, correct? So, if this is the case does the nerve in the tooth serve a function (except for the sensitivity purpose)? Is this the only thing done in a root canal? If the nerve tissue does not serve a purpose, what ist the point of removing it (except to alleviate pain/sensitivity issues)? What other goals are accomplished in a root canal procedure, except removing the nerve tissue and replacing with a bonding fluid?

I'm looking for somebody to thoroughly explain a root canal procedure to me. Why are they needed? What are the expected results?