What's next for the UEFA Nations League and what does it mean for EURO 2020?

The group phase of the inaugural UEFA Nations League has now concluded, with all the promotion, relegation and play-off issues resolved.

It's fair to say that the new competition has proved pretty exciting, with small group formats in the elite League A going right down to the wire.

England, for example, went from facing relegation to a place in the Nations League finals thanks to two goals in seven minutes against Croatia on Sunday.

And Holland came back from two down with just five minutes remaining to draw against Germany and book their finals spot at the expense of France.

So what happens now? And what will the next Nations League in 2020 look like? Sportsmail explains all.

LEAGUE A

How did it unfold? Naturally, the top League attracted most of the attention with 12 of Europe's top-ranked nations battling it out to reach the final four or avoid relegation.

With just three in each group, there was no margin for error and that made for plenty of twists and turns as the competition unfolded.

England finished top of a fiendishly tricky group featuring Spain and World Cup finalists Croatia, beating both in their final two matches.

At Wembley last Sunday, Gareth Southgate's team went from staring relegation in the face to finals qualification in the space of seven giddy minutes late on.

The surprise package were Holland, revitalised under new coach Ronald Koeman. They beat Germany 3-0 and France 2-0 at home, before a last-gasp smash and grab earned a decisive draw away to Germany on Monday night.

That put them through to next summer's finals on head-to-head record at the expense of France, with Germany experiencing a humbling relegation into League B.

Another incredible fightback saw Switzerland come back from two goals down to beat Belgium 5-2 and top their group, again by virtue of a superior head-to-head record.

And Portugal, who will host next June's finals, topped their group ahead of Italy.

What happens next? England, Holland, Switzerland and Portugal will contest the Nations League finals in June next year.

There will be two semi-finals, a final and a third place play-off, all to be staged in the Portuguese cities of Porto and Guimaraes between June 5 and June 9 next year.

The draw for the semi-finals will be made in Dublin on December 3 and the team that wins the final will become the first-ever Nations League champions.

In addition, the four group winners are assured of a play-off place for Euro 2020 should they not make it through the normal qualifying. More on that below.

Teams relegated: Germany, Iceland, Poland and Croatia will drop into League B for the next instalment of the Nations League starting in the autumn of 2020.

LEAGUE B

How did it unfold? In the second-tier, we saw Ukraine, Sweden, Bosnia-Herzegovina and Denmark secure promotion to League A for the next tournament in two years' time.

Denmark finished top of a group containing Wales and the Republic of Ireland. Ryan Giggs's side had to settle for second place when Denmark beat them 2-1 in Cardiff last week.

They did, however, twice defeat Ireland - 4-1 at home and 1-0 away - as Martin O'Neill's side dropped into League C next time. O'Neill and assistant Roy Keane have since stepped down from their jobs.

Northern Ireland didn't fare any better, losing all four of their matches to finish below Bosnia and Austria in their group and slide into the third-tier.

There was a good finish in Group Two, where Sweden's 2-0 home win over Russia on the final matchday earned them promotion at their opponent's expense.

Promoted to League A: Ukraine, Sweden, Bosnia-Herzegovina, Denmark

Who's into the play-offs? The Nations League also acts as a means of earning qualification for Euro 2020.

The main qualification campaign for the tournament will run from March through to November 2019, with the draw set to be held on December 2 this year.

However, the teams who have finished top of their groups in Nations League B, C and D have gained themselves a failsafe should they not qualify through the normal route.

So as it stands, the four group winners in League B - Ukraine, Sweden, Bosnia and Denmark - have a guaranteed place in the Euro 2020 play-offs, which will be held in March 2020.

However, if they qualify anyway, their place will be allocated to teams from another league, depending on their records.

That won't become clear until November next year though when the normal qualifying has been concluded.

Relegated to League C: Slovakia, Turkey, Northern Ireland, Republic of Ireland

LEAGUE C

How did it unfold? We saw Scotland, Finland, Norway and Serbia win promotion from the third-tier to the second as well as guarantee themselves a play-off spot for Euro 2020.

Scotland's 3-2 win over Israel at Hampden Park on Tuesday night assured their upgrade in the next Nations League in 2020 as they won three of their four matches.

Promoted to League B: Scotland, Finland, Norway, Serbia

Who's into the play-offs? Those four group winners are assured of a play-off spot should they not make it out of their Euro 2020 qualifying group.

A bit more detail on how the play-off allocations work now. The 16 teams that will enter the Play-offs will be chosen starting with League D and working up to League A.

1. All available group winners will be selected, hence the bonus of topping your Nations League group.

2. If a group winner has already qualified through the normal qualification process, their place will be given to the next best-ranked team from the same league that hasn't already qualified.

3. If fewer than four teams from a given league have failed to qualify, then the remaining spaces for that league will be allocated by overall Nations League rankings.

Relegated to League D: Estonia, Cyprus, Slovenia, Lithuania. Cyprus finished third in their group but because of an uneven number of teams in League C, one relegation spot was decided by which third-placed team had the worst record.

LEAGUE D

How did it unfold? The bottom tier of the Nations League featured all the minnows, with Georgia, Belarus, Kosovo and Macedonia achieving promotion and assuring themselves of a play-off spot.

Gibraltar were in contention for promotion having recorded wins over Armenia and Liechtenstein, but heavy losses in their last two matches ended those hopes.

Promoted to League C: Georgia, Belarus, Kosovo, Macedonia

Who's into the play-offs? The four teams above, none of whom have ever qualified for a major tournament, will be very excited by their guaranteed play-off spot for Euro 2020.

It really is a great opportunity for one of the lesser lights of European football to qualify for the finals.