The fundamental difference between CSV and TEXT formats is how characters are escaped.
With CSV, characters such as the field delimiter, the quote character, or the end-of-record are escaped by placing the QUOTE character before and after the character that needs to be escaped. i.e. "," would allow you to have a field that contains a comma in a file that uses commas as the field separator.
With TEXT, characters are escaped by proceeding them with the escape character. This is typically done with a backslash. i.e. \, would allow a comma in a field.
There are also differences in the default values of used for field separators, end-of-record, and quote characters. However, those can all be changed.
The file extension is not used to specify the file type.
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