The Pokémon Browser, accessible through your Ranger Net, acts as your in-game Pokédex. It records information about every Pokémon you've captured, including their Field Moves and typical habitats. Completing the Pokémon Browser is a significant side activity for completionists.
To complete the Browser, you'll need to capture every unique Pokémon in the Fiore region. This often involves revisiting areas with different Pokémon spawns or exploring hidden paths. Some rare Pokémon might only appear under specific conditions or after certain story events. While there isn't a direct in-game reward for 100% completion beyond the satisfaction, it's a great way to experience all the diverse Pokémon the game has to offer and master various capture techniques.
Keep an eye out for Pokémon you haven't captured yet, indicated by a '???' entry in your Browser. Happy hunting!