What is the Nations League all about?
UEFA have introduced this tournament to give national teams more competitive matches and fewer meaningless friendlies.
It has a group stage, a final tournament and a trophy for the winner.
What is the format?
The 55 European countries have been split into four leagues — A, B, C and D — based on their UEFA ranking.
As England are one of the 12 best-ranked sides, they are in League A.
Each league has been split into four mini-groups, with England pitted against Spain and Croatia in Group 4.
What happens if we win our group?
Top the group and England will advance to the Nations League finals with the three other group winners from League A.
In December, one of these four will be picked to host the final tournament.
In June 2019, the teams will take part in semi-finals and a final to crown the first Nations League champions.
But what if we finish bottom?
Finishing bottom would see England relegated to League B. For the likes of Wales and Northern Ireland who are in League B this year, winning their mini-group would mean promotion to League A.
There is also promotion and relegation between Leagues B-C and C-D.
Can teams qualify for Euro 2020 through the Nations League?
They can. Four teams will qualify via the Nations League play-offs and join the 20 teams who will take their places for Euro 2020 through a qualifying group as normal.
How do the play-offs work?
The four mini-group winners from each of the Nations League tiers — A, B, C and D — will contest a one-off semi-final, followed by a final, in March 2020.
The winners of the play-off final in each of the four leagues will then qualify for Euro 2020.
It means that if England beat Spain and Croatia to the top of their mini-group this autumn, they could still go on to claim a play-off place for Euro 2020 even if they mess up in their qualifying campaign next year.
What if England do not require the play-offs?
If England win their Nations League group this autumn but also finish in the top two of their qualifying group next year, their play-off place will go to the next best Nations League side who have not already qualified.