This is a new tournament, largely replacing international friendlies in certain parts of the soccer calendar. UEFA intends to hold this every other year. All 55 national teams are participating.
The teams are divided into four leagues, based on rankings around the last World Cup. The top dozen are in League A, the next 12 League B, and so on (though more than a dozen in C and D each). The Leagues are in turn each divided into equal cross-section Groups of three or four. In each Group, the teams will play home and away double round robins.
In League A, the four winners will have a Playoff to determine the event champion. In the other leagues, the Group winners will have a Playoff as well. The winners of all four Playoffs automatically qualify for the 2020 European Championships.