His proposal is for Trump to meet privately with Supreme Court justices who are interested in retirement. If one of those justices decided they would be willing to retire, and if Trump promises to nominate Garland, President Barack Obama's unconfirmed former SCOTUS pick, in their place, then the retiring justice would submit a letter of resignation contingent on that promise.Then, both Garland and Gorsuch would be voted on simultaneously.
The best thing about this is there won't be a war over which way the Court will lean when Ruth Bader Ginsburg retires. Also it blunts the Dem attack that is valid that Garland didn't get a fair shake when Obama nominated him. That decision to not even meet with Garland will come back to haunt the GOP in the future. This move also feels like a very bi-partisan and might even heal some of the division in Washington.