Technical/ in-depth alloy question - 18-8 vs 304 vs 300 series stainless steel

Can anybody explain what these technically/officially encompass? Most websites and resources use these terms differently and I can’t find a consensus.

Is 18-8 an exact alloy of (stainless) steel, the old school name for 304SS, or a family of alloys with a minimum percentage requirement of each element? Does 18-8 mean it could be 18-8, 304, or 316?

Does 300 series mean it needs to be 301, 302, 303, 304, 316, etc but NOT 18-8 or does it also include 18-8?

Engineer TL;DR I need/want a Venn diagram that contains 18-8, 304, 316, 300 series, & generic “stainless steel” so I can understand what falls “inside” of 18-8 & 300 series.