Minor Races are those races who are not Major Races and were not geneered by others, except possibly the Ancients. That is, have been living on a world from before the Vilani got jump drive and have not independently developed faster than light travel. Geneered races are sometimes erroneously called Minor, but the proper term is Variant. Numerous minor races exist, some have been fully developed, some only briefly mentioned, in the Traveller background material. Minor Races can exist at all levels of technology and may have acquired faster than light travel from all sorts of sources from traders, or even reverse engineering ancient technology.
There are about 100 intelligent races in the Imperium and about 400 in Charted Space, but these figures do not included Minor Human Races or variants.