What's the difference between using application/csv
vs text/csv
as the HTTP Accept Header?
A MIME type is used so software ( like a browser for example ) can know how to handle the data.
If a server says "This data is of type text/csv" the client can understand that can render that data internally, while if the server says "This data is of type application/csv" the client knows that it needs to launch the application that is registered on the OS to open csv files.
text/csv is more generic.