Best described in the words on the FileHelpers website:
The FileHelpers are a free and easy to use .NET library to import/export data from fixed length or delimited records in files, strings or streams.
It is a library that can be used to work with flat text files (e.g. Comma Separated Value (CSV) or Tab Separated Values (TSV) etc). Available for commercial and non-commercial use (under the LGPL). They also have a blog.
There is also a CSV parser on CodeProject if you can't use a library licensed under the LGPL: A Fast CSV Reader. Not as powerful as FileHelpers but still good nonetheless.