The new online feature builds upon the Trainer Battle system
Last December, Pokémon GO launched the high anticipated Trainer Battle feature, finally letting trainers battle each other outside of the gym system. The PvP system was only available to trainers within the same physical area and using similar CP leveled Pokémon.
The developers of Pokémon GO, Niantic, announced via a post on the Pokémon GO website that an online version of the Trainer Battle system will be launching early 2020 called GO Battle League.
Much like the mainline series Pokémon game, the GO Battle League will have an online matchmaking system based on your current rank in the league. Winning trainer battles online will let you raise your rank. To gain entry to the GO Battle League, trainers must walk with their Pokémon in real life, though the full details of this haven't been revealed at this time. The rewards for the online league haven’t been announced just yet, with more details to be released as the launch date approaches.
Source: Pokémon GO Website
Daryl Harding is a Japan Correspondent for Crunchyroll News. He also runs the YouTube channel about Japan stuff called TheDoctorDazza, tweets at @DoctorDazza and posts photo of his travels on Instagram.