there are ancestries, which are like dnd races/species

then there are heritages, which are like subraces/subspecies

and there are versatile heritages, which any ancestry can take.

for example, there’s nephilim, which means you have some celestial or fiendish being influence (it’s the pf2e remastered version of tieflings and aasimars). it lets you choose one out of a bunch of different types of fiends and celestials through lineage feats (which are kind of subsubspecies).

there’s also dhampir, which means one of your parents was a vampire, and it lets you choose through a lineage feat what kind of vampire they were.

and there are some that don’t have lineages, like hungerseed (half-oni), and duskwalker (reborn with a connection to death or something, it’s complicated)

and finally, there’s aiuvarin (half-elf) and droomar (half-orc), which let you choose from all feats from your ancestry + elf or orc respectively. the rules allow you to create your own custom mixed ancestry, which work the same way, you just need to work with your GM to create feats that only work for those who are only half of that ancestry (both aiuvarin and droomar include feats that pure elves and orcs can’t take)

if you want more specific details:
Mixed Ancestry rules https://2e.aonprd.com/Rules.aspx?ID=2093

List of Versatile Hertiages https://2e.aonprd.com/Ancestries.aspx?Versatile=true

edit: forgot 2 words