Foreigners in the U.S. who want a green card will now have to leave the U.S. and apply in their home country. This is a change into a long-standing system where people already living in the U.S. could apply for green cards while still in this country. https://texasstandard.org/stories/trump-administration-green-card-application-change/
What the new Trump administration directive on green card applications means

Applicants have been told to return to their home country to start the process.

Texas Standard