FYI Full Form is For Your Information. The term is most commonly used in emails, messages, chats, etc. FYI is used before any message so that reader always remember it.
FYI has been in use since 1941. FYI it is an acronym and is also very much discussed in the internet world. It is more and more used when sending emails to companies.
How To Use FYI Correctly
FYI, I am sending you some PDF files related to that software engineering notes.
FYI, our internet connection was offline from 11:00 pm.