What is csv?

CSV stands for Comma Separate Values. If you load the data in notepad, it might look something like:

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The file would generally have a .CSV suffix at the end of the filename to let packages such as Excel know what sort of data is contained and how to deal with it.
(Excel has an XLS suffix, Word a DOC suffix, Notepad a TXT suffix. You might not be able to see the suffixes unless your PC has been configured to view them.)

Now if you load the same data into Excel, Cell A1 = 1, B1=212, C1=44, D1=24, E1=4, A2=2, B2=3 and so on. The only difference is that there would be no formatting in a csv file; it is text ONLY separated by commas. You can also get Tab Delimited Files, Space Delimited Files, Tilde (~) and pretty well anything else you could choose. Excel will read them all ignoring the delimiters and placing the rest of the data into unique cells.

Unless a person is involved in the automated sharing of data via a database/software package, then it's eally not worth bothering much with it as a format although it's worth knowing that csv's exist.

I hope this helps.