A root canal is a dental procedure that uses special tools and techniques to remove the deep, central portion of the tooth called the pulp. The pulp is the living portion of the tooth that extends all the way down to the roots through channels or canals. When the pulp becomes decayed or damaged, a root canal can remove the damaged pulp and fill the canal so the tooth doesn't need to be extracted.
You could have a badly decayed tooth pulled, but generally speaking, it's always better to try to save a natural tooth. Your teeth work in pairs – upper and lower – and when you lose a tooth, it can cause problems with your bite that can result in uneven tooth wear. Plus, when a tooth is missing, the jaw bone that supports the tooth will begin to atrophy, causing neighboring teeth to “lean in” to the gap, causing weak roots and, eventually, additional tooth loss.