Protect/Detect are essentially a "blank turn", but end-of-turn actions still occur. Here are several reasons Protect/Detect may be used:
- Recovering HP if you are holding Leftovers (or similar set-ups like the move Ingrain).
- Ability gains such as from Speed Boost.
- Opponent taking damage from a burn or poison.
- Opponent taking damage from a weather condition.
- If the opponent is confused, there is an extra chance they could hurt themselves in confusion.
- Protecting against two turn attacks like Dig or Fly. Because those moves attack on the second turn you know they are coming and Protect will work every time.
- In double/triple battles, you can avoid damage from teammates using moves such as Earthquake or Surf.
- Wasting the opponent's PP. For moves like Hydro Pump that only has 5 PP (or max 8) it could be vital.
- "Scoping out" the opponent's moves - in other words, checking what moves your opponent has.
If one or more non-protect moves are used between each use of Protect/Detect (for example on alternate turns), they are guaranteed to work.
Are all Ghost-type Pokémon the ghosts of Pokémon? Certainly not. Best way to sleuth this out is simply to read Pokédex entries on Bulbapedia (reading them all in-game would require about a dozen games):
Gastly:
Born from gases, anyone would faint if engulfed by its gaseous body, which contains poison.
Yamask:
Each of them carries a mask that used to be its face when it was human. Sometimes they look at it and cry.
Banette:
A doll that became a Pokémon over its grudge from being junked. It seeks the child that disowned it.
Phantump:
According to old tales, these Pokémon are stumps possessed by the spirits of children who died while lost in the forest.
Ghost-type Pokémon are a collection of beings that are either literal ghosts (Yamask), poltergeists (Banette) or simply unusual beings that have properties similar to ghosts (Gastly). Some, but not all, Ghost types can actually be ghosts of Pokémon though. Drifloon is the only one I've found:
Drifloon:
A Pokémon formed by the spirits of people and Pokémon. It loves damp, humid seasons.
Most Ghost types are simply referred to as being "spirits" that inhabited some sort of object or spontaneously generated some sort of body. "Spirits" is usually left ambiguous, though several entries specifically mention human spirits, and fewer mention Pokémon spirits. And many simply have no explanation for their existence (Duskull and Misdreavus. And Frillish which doesn't even make mention of any ghostly properties at all other than a grim malice).
The anime apparently has a "Ghost World" which is a home to Ghost Pokémon, which is implicitly the one mentioned in Dusknoir's Pokédex entries:
The antenna on its head captures radio waves from the world of spirits that command it to take people there.
Best Answer
Whirlwind has a different effect in trainer battles vs. wild battles. Against trainers in the first generation game, it has no effect. Starting in generation 2 trainer battles, it forces them to switch out to a new pokemon at random. If they have no other pokemon, it has no effect.
No pokemon typing will cause immunity, but the ability Suction Cup or the move Ingrain will cause it to fail.