The values are:
vw (% of the viewport width)
vh (% of the viewport height)
vi (1% of the viewport size in the direction of the root element’s inline axis)
vb (1% of the viewport size in the direction of the root element’s block axis)
vmin (the smaller of vw or vh)
vmax (the larger or vw or vh)
1 v* is equal to 1% of the initial containing block.
using it looks like this:
As you can see, when the viewport width increases, so does the font-size, without needing to use media queries.
These values are a sizing unit, just like px or em, so they can be used to size other elements as well, such was width, margin, or padding.
Browser support is pretty good, but you’ll likely need a fallback, such as: