The domain of a quadratic function is the set of all possible input values (x-values) for which the function is defined.
For the given quadratic function:
\( y = x^2 - 8x + 16 \)
This is a polynomial function, and polynomial functions are defined for all real numbers. Therefore, the domain of the function is:
\[ \text{Domain} = (-\infty, \infty) \]
In interval notation, this means that you can plug any real number into the function for \( x \).