DR is a third-party metric, not something Google uses. Moz's Domain Authority (DA) and Semrush's Authority Score are similar.
Because the scale is logarithmic, going from DR 70 to 80 is much harder than going from 10 to 20.
Why it matters when you launch
DR is a quick way to prioritise directories. A link from a DR 80 site is generally worth more than one from a DR 20 site, but relevance and real traffic matter too.