(This is from an article by David Platt and David Burnett, see link below). Unreached people and places are those among whom Jesus is largely unknown and the church is relatively insufficient to make Jesus known to its broader population without outside help. The plight of the unreached helped motivate the apostle Paul’s missionary efforts:
“I make it my ambition to preach the gospel, not where Christ has already been named, lest I build on someone else’s foundation, but as it is written, “Those who have never been told of Him will see, and those who have never heard will understand.” – Romans 15:19-21
Read the article here: https://radical.net/article/unreached-hard-to-reach/?amp=1
If you are not familiar with the term “10. /40 Window”, here is a brief video on that subject from thewaitingworld.net. Click on the link below to watch it: https://www.dropbox.com/s/44bhh8bk1e6huci/1040%20Window%20WW%20copy.mp4?dl=0