Question

What does f(x)=3 mean?

Answer 1

It means that you have a function that every time you input a value of `x` gives you `3`.
If `x=45` then `y=3`...if `x=-1.234` then, again, `y=3` and so on!
It is like to take a bus that charges a fixed fee of $ 3 regardless of the duration of the journey...you can say "I want to go to this or that stop (this is the `x`)" it doesn't matter...you'll alway pay $ 3 (that is the `y`).