A root canal is a procedure done to remove the infected or inflamed pulp of a tooth and replace it with a sealing material. A back tooth receiving a root canal will usually need a crown, while a front tooth can often be restored with a cosmetic white filling. A dark front tooth with a root canal can sometimes be whitened on the inside using a procedure called "Internal Whitening" for a more beautiful and conservative result. See examples of internal whitening under the section "View Dr Raber's work".
The only alternative to a root canal is to extract the tooth (or live with the infection, which is not healthy for the body). While this option is cheaper in the short term, the long-term consequences can be quite costly.
More than 95% of properly done root canals are successful. Millions of teeth are treated and saved each year with root canals, or endodontic, treatment. Remember, root canal treatment doesn't cause pain, it relieves it.