landrace strains

I read about certain strains of weed labeled "landrace" strains, afghani being one of them, whats that mean exactly?

The only thing I could think of is that its a wild growing weed and theres fields and fields of it somewhere and it's all pure, same genes for years and years and never crossed with any other type of strain.

From Wikipedia:

Landrace refers to domesticated animals or plants adapted to the natural and cultural environment in which they live (or originated) and, in some cases, work; they often develop naturally with minimal assistance or guidance from humans (or from humans using traditional rather than modern breeding methods), hence differ somewhat from what is commonly termed a breed, and usually possess more diverse phenotypes and genotypes. They often form the basis of more highly-bred formalised breeds. Sometimes a formalised breed retains the "landrace" name, despite no longer being a true landrace.