The acronym fyi stands for "for your information".
Its use is to inform someone about anything and placing the acronym as a starter to a sentence or to end it.
e.g. Fyi, I'm not gonna make it tonight, sorry.
Hey, fyi, I
don't want to watch this movie.
I
don't think that we're gonna be there on
time, fyi.
The use of it is not strict and you can form variations on how fyi will be used in a sentence. As
long as its meaning doesn't change.