We don't know. It's a Pokemon's view.
<------------- Inside of a Poké Ball
>Poké Balls are specifically constructed for Pokémon capture, transport and training. As well as being physically difficult to escape from (as they seal tightly shut as soon as a Pokémon is taken into them) the environment of a Poké Ball is designed to be attractive to Pokémon also; according to Lucian of the Sinnoh Elite Four, weakened Pokémon instinctively curl up tight in an attempt to heal themselves, an action that the environment of the Poké Ball encourages. Furthermore, while it is not known how a captured Pokémon perceives their time inside their Ball, the device is said to replicate a "Pokémon-friendly" environment that is "designed for comfort". All of these factors strongly discourage Pokémon from escaping their Balls.
Apparently, the Poké Ball seems to be comforting; encouraging the Pokemon to heal. However, there are exceptions, such as Ash's Pikachu, who hates being in a Poké Ball.
Source: Bulbapedia- Poké Ball