Domain: −∞ < x < ∞ or (−∞, ∞)
Range: 0 ≤ y < ∞ or [0, ∞)
The domain of a function is the function's possible inputs, the x, of the function. Here, any number can successfully be plugged into f(x), so the domain is all real numbers.
The range of a function is all of its possible outputs, the y, of the function. Here, anything greater than or equal to 0 is a possible y value of f(x). This means our range is anything greater than or equal to 0.
I have graphed f(x), see attached for the graph of | x - 3|.