What is the domain of the following function?

Let's use these two sets given to explain what is the domain.

Each value from the left set is x, and from the right is f(x).

If we plug any x from the left set in the function, we'll get f(x)  that corresponds to it and that's exactly what the arrows are showing.

Domain of the function is, basically, a set of all values x can have.

In this case, it's easy to see, those are all members of the left set (-6, 1, 5, 8), but sometimes this set can have lots and lots of members, even infinity.

answer: what do you mean