What is a CSV file?

Someone else will have an answer that is more technically correct. The simple version: CSV is one format for capturing information so that standard software packages can import it.

When I download my wish list, I want to be able to manipulate it in Excel.
The data (fields, columns) for one item (record) in the wish list (title, author, ISBN10 and ISBN13) are separated by commas so Excel can parse data into columns.

edited for some clarity

Yes, Mary had it right.

When I went to Yahoo and typed in csv file, it returned with this link.....http://www.creativyst.com/Doc/Articles/CSV/CSV01.htm

Comma Separated Values. It's a means of saving a file in a very generic form where each value is separated by a comma. Pretty much any computer program can read this because it's literally just vanilla text - no formatting at all. It's used a lot with databases, Excel, and report programs.

It's a handy way to save the data with one program and assure you'll be able to read it/tmport it with something else.