Quoting from the first source that I could find (PDF), at the top of ยง8.3 Common Functions, page 132:
These all operate component-wise. The description is per component.
Nearly all the functions that operator on vectors but really only make sense for a scalar operate component-wise. (This includes abs, sign, floor, trunc, round, roundEven, ceil, fract, mod, modf, min, max, clamp, mix, step, smoothstep, and a whole lot more.)
So, for example, the min of (1, 3) and (4, -2) is (1, -2).