What is a flat file? what feartures do these have?

Answer 1

A flat file ? In relation to WHAT ?

Other than having other info I'd suggest a file that got run over !

Answer 2

Flat file, sometimes means
"flat text file"
or a plain text file

a file that can be dragged into notepad and viewed as plain text.

for example, a flat text database would be plain text (not nexcessicarily .txt extension) but entries would be
001 data
002 data
003 data
004 data

instead of a coded language