The domain of a function is often specified by using interval notation. For example, the domain of the function f(x) = x^2 is (-∞, ∞), which means that the function is defined for all real numbers.
The domain of a function can also be specified by using set-builder notation. For example, the domain of the function f(x) = 1/x is {x | x ≠ 0}, which means that the function is defined for all real numbers except for 0.
The domain of a function is important because it tells you what values you can input into the function. If you input a value that is not in the domain, the function will be undefined.