When the Data Import tool validates a file, the database checks to make sure all column headers are correct, all data is in the correct format, and all information that needs to be in the database is already there. When the Data Import tool processes a file, it also validates the file. And, if the validation is clean, the file is processed and the data is inserted into the database.

Note: It is good practice to validate the file first until it is cleanly validated and then process it.