When we're talking about functions in Algebra I, it's super important to understand the difference between domain and range.

• Domain: This is all the possible input values (or $x$ values) that a function can take. For example, in the function $f(x) = \sqrt{x}$, the domain is $x \geq 0$. This means we can't take the square root of a negative number, so we only use zero and positive numbers.

• Range: This is all the possible output values (or $y$ values) that a function can give us. Using the same example, the range of $f(x) = \sqrt{x}$ is also $y \geq 0$. That’s because the square root will never give us a negative number.

To sum it up, you can think of the domain like the street where you start (the inputs) and the range as the places you can go (the outputs).