What does it mean when a Pokémon has a white ring around it?

What does it mean when a Pokémon has a white ring around it? This ring is an indicator of the level to which that PokéStop or Gym has been powered up. Each PokéStop or Gym can be powered up to levels 1, 2, or 3, with each subsequent level providing more powerful or valuable items. PokéStops powered up to higher levels will also sustain these benefits longer.

This ring is an indicator of the level to which that PokéStop or Gym has been powered up. Each PokéStop or Gym can be powered up to levels 1, 2, or 3, with each subsequent level providing more powerful or valuable items. PokéStops powered up to higher levels will also sustain these benefits longer.