[Trigger] One question about a wierd trigger

[Shanghai]

• Unit Group - Pick every unit in TempGroup and do (Actions)
  • Loop - Actions
    • If (All Conditions are True) then do (Then Actions) else do (Else Actions)
      • If - Conditions
        • (Unit-type of (Picked unit)) Equal to Dummy Unit 1 Self Kill
        • ((Owner of (Picked unit)) slot status) Not equal to Is playing
      • Then - Actions
        • Unit - Remove (Picked unit) from the game
      • Else - Actions

Exactually what does this trigger do?

 

[Marsal]

Picks every unit in the temp group then if the unit equal to the Dummy Unit 1 Self Kill and the owner of it is not playing (so left the game or just an empy slot or a comp) removes the unit

 

[Elite Slayer]

Just elaborating on what Marsal2000 said

What the trigger you have posted does, is it selects every single unit in the unit group variable Temp Group (the variable's name tells us that the units in this unit group may change, since it's a temporary ("temp") unit group), and it checks each unit against the following conditions:
• Whether the unit-type of the unit is equal to Dummy Unit 1 Self Kill or not. In other words, it looks to see whether the unit it's examining is a 'dummy unit 1 self kill.' In order for it to "pass" this "test", the unit has to be a 'dummy unit 1 self kill.'
• Whether the owning player (the human/computer owner of the unit) is playing or not. After all, s/he might have left. In order for it to "pass" this "test", the owner of the unit must not be playing, or must have left the game.

If the unit the trigger is examining matches the two conditions ("passes" the "tests"), then that unit is removed permanently from the game.

I hope this helped!
And thank you to Marsal2000 for providing an accurate answer on which to base mine. Will be sure to +rep him.