A CSV (comma separated values) file is a basic version of a collection of data - with no extras or fancy formatting. Each field is separated by a comma. Since many applications use non-standard file formats (think of them speaking different languages), CSV files act as a universal format that enables you to see your data in a variety of applications, including Microsoft Excel, Numbers, Apache OpenOffice.org Calc, Google Spreadsheets and more.
If you do not have Microsoft Excel or Numbers, we would recommend you to either use open Apache OpenOffice.org or Google Spreadsheets.
Tips:
Excel tip #1 - Some programs will import your data and combine fields like first and last name in the same column. If this happens to you, be sure to select "space" and "comma" separators in the options provided when opening a CSV from an outside source. This will separate your data into different columns instead of bunching up all the information in one single field.
Excel tip #2 - Replace (Ctrl + h). Sometimes imports can get stuck because your files are full with unwanted punctuation. Think of Replace as seek and destroy for errant characters. In the Edit menu select Replace or hit Ctrl + h on your keyboard, in the “Find What:” field type in whatever it is you want to mass replace, leave the “Replace With” field blank and click “Replace All”.
Excel tip #3 - Save your CSV file in Unicode UTF-8 format, as that is the default for most online databases.