"Lottery, think of the lottery. You have a country, they put names in, you think they're giving us their good people?" Trump asked rhetorically. "So we pick out people, then they turn out to be horrendous and we don't understand why."

This is, of course, not how the diversity visa lottery works. Every year, the United States reserves 50,000 visas for prospective immigrants from nations that have not sent many immigrants to America in the past (in many cases, because those nations were barred from sending immigrants to the U.S. for much of the 20th century, due to explicitly racist immigration laws). Millions of people apply for those slots, and the field is winnowed through a lottery. But these immigrants are self-selected (not appointed by their governments as Trump suggests), and must meet America's stringent education and work experience requirements for all newcomers, and then undergo vetting by the State Department before entering the country (as opposed to being immediately flown to the United States, no questions asked, as Trump implies).

Anyhow, in these remarks, Trump argues that the winners of the diversity lottery "turn out to be horrendous" - meaning, once they arrive in this country and become American residents or citizens, they reveal themselves to be universally horrible.