You have likely heard of Unreached People Groups (UPGs)—ethnic groups of peoples where the number of self-professing Christians is under 5% of the population.
Unengaged UPGs (UUPGs) are those groups the church has not yet attempted to reach. They still lack any kind of witness among them, and there is not even a plan to create one. There is no way they could hear about Jesus unless someone crosses a cultural barrier to bring them the good news.
Now there’s a new term circulating among missiologists: Frontier People Groups (FPGs). While the definition is still in flux, the label was added to make a distinction between UPGs where God has begun a work, and those groups yet to experience their first church.