The minmax() CSS function is used to set a minimum and maximum length of a
grid. It accepts 2 arguments minimum value and maximum value. It is very
useful for creating responsive layouts when combined with relative units like
fr.
Let's look at some examples:
minmax(100px, 1fr) the width of the first column remains minimum 100px or
at max 1fr, so it changes according to the width of the screen.
Try resizing your browser window, to see it in action.