Wales will play a 3rd place team from Group A, C or D. Albania have already finished 3rd in Group A with 3 points and a -2 goal difference. Here is how Groups C and D look before the final fixtures today, and what could happen.
Group C - 5pm, BBC1 Germany 4pts +2GD
2 Poland 4pts +1GD
3 Northern Ireland 3pts +1GD
4 Ukraine 0pts -4GD (already eliminated)
Northern Ireland v Germany
Ukraine v Poland
Germany will progress to the next round if they avoid defeat against Northern Ireland. They will win the group if they win, unless there's a two goal swing in GD between them and Poland. Germany will finish 3rd if they lose and Poland win.
Poland will go through if they avoid defeat against Ukraine. As said above, if both Germany and Poland both win then Poland will need a two-goal swing to win the group. They will also win the group if they win and Germany fail to win. Poland will only finish 3rd if Northern Ireland beat Germany, and they lose to Ukraine.
Northern Ireland need to win to stand any chance of making the top two. If they fail to do that, they will finish 3rd.
So, all the possible 3rd place finishes are:
Germany 4pts
Poland 4pts
Northern Ireland 3pts or 4pts
Group D - 8pm, ITV1 Spain 6pts +4GD
2 Croatia 4pts +1GD
3 Czech Republic 1pt -1GD
4 Turkey 0pts -4GD
Spain have qualified for the last 16. If they avoid defeat against Croatia, they will win the group. If they lose, Croatia will win the group.
As said above, Croatia will win the group if they beat Spain. They will qualify in 2nd place if they draw. If they lose, Czech Republic win and there is a three-goal swing in goal difference, then Croatia will finish 3rd.
Turkey can't make the top two. They will finish 3rd if they beat Czech Republic, but anything else would see them finish bottom of the group.
So, all the possible 3rd place finishes are:
Croatia 4pts
Czech Republic 2pts or 4pts
Turkey 3pts
We will then have to wait until tomorrow night to see who the four best 3rd place teams are. Here is who we will next, dependent on which groups have the four best 3rd place teams. The successful groups on the left.
A, B, C, D - Group D 3rd - Croatia, Czech Republic or Turkey
A, B, C, E - Albania
A, B, C, F - Albania
A, B, D, E - Albania
A, B, D, F - Albania
A, B, E, F - Albania
B, C, D, E - Group D 3rd - Croatia, Czech Republic or Turkey
B, C, D, F - Group D 3rd - Croatia, Czech Republic or Turkey
B, C, E, F - Group C 3rd - Northern Ireland
B, D, E, F - Group D 3rd - Croatia, Czech Republic or Turkey
C, D, E, F - Group D 3rd - Croatia, Czech Republic or Turkey
I hope that was clear