Why do we need XML parser?

We need XML parser because we do not want to do everything in our application from scratch, and we need some "helper" programs or libraries to do something very low-level but very necessary to us. These low-level but necessary things include checking the well-formedness, validating the document against its DTD or schema (just for validating parsers), resolving character reference, understanding CDATA sections, and so on. XML parsers are just such "helper" programs and they will do all these jobsl. With XML parsers, we are shielded from a lot of these complexicities and we could concentrate ourselves on just programming at high-level through the API's implemented by the parsers, and thus gain programming efficiency.