"Trainer" definition

[Muscovy Level X]

This is probably a silly question, but at league there have been so many disagreements (a few on here too), about the definition of "trainer" "Stadium" and "Supporter".
I know that when a PK- card says search for a "trainer", it can be any PK- "Trainer" "Stadium" or "Supporter". So only the plain trainers in DP+ can be searched for by a PK- card?
And what about getting PK- cards from a DP+ searcher? If it says "trainer" does that mean you can get any PK- Trainer card?

 

[PokePop]

A PK- card that does things with Trainers can do them with Trainers, Supporters, or Stadiums. They are all Trainers to it. There is no difference to them.

A DP+ card "knows" the difference. So if it does something with Trainers, it can't do it with any Supporter or Stadium, even if they are older ones and have Trainer printed on them. The DP+ card "knows" that they are not really Trainers.

Look at it from the cards point of view and you will be able to keep it straight.