The competition, which Uefa say will replace "most friendlies" in global football, is due to begin on 6 September 2018, and will separate teams according to how they are ranked.
The Azerbaijani national football team will play in the fourth division of the UEFA Nations League that starts next year.
The other 43 European nations will be spread across three other Leagues B, C and D - the group winners will be promoted to replace the nations finishing bottom of Leagues A, B and C for the next Nations League which begins in September 2020.
That means missing out on the potential for games against Germany, Italy, Spain and England, who are among the dozen teams to qualify for League A. The four group winners will be promoted to League B, with the four bottom sides relegated to League D for the 2020 edition.
The top 12 nations, based on the 2017 UEFA National Ranking, are in League A will be drawn into four groups of three and play each other home and away on the global dates in September, October and November next year.
League D features 16 teams, with four groups of four, and those teams will play on all six assigned matchdays. "One host country will be appointed in December 2018 from among the finalist teams", explained the governing body on its official website.
Teams will be split into one group of three and three groups of four. Promotion will not take place until the second edition of the tournament in 2020.
Teams will be drawn into four groups of four.
Wales have missed out on a place in the top league of Uefa's new Nations League tournament after losing their final World Cup qualifier.
Each season of the UEFA Nations League will be played from September to November of an even-numbered year (pool stage), and June of the following odd-numbered year (final four competition of League A).
The Euro 2020 qualification play-offs are set for March 2020 as mentioned above, and Euro 2020 itself, which will be played across the continent, will begin three months later.