If you pay for the service, you'll be able to bring over your Pokémon from linked games and deposit them into the app or move them around to another compatible game.
Compatible games include Pokémon Sword and Shield, and Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!. You can also connect to the Pokémon Bank on Nintendo 3DS, and connectivity with the Pokémon Go app is coming sometime after launch.
The Pokémon Home app opens up the catalog of available Pokémon in the latest Sword and Shield games, by allowing you to transfer Pokémon from Nintendo 3DS games into Home, and then into Sword or Shield. Once Pokémon are transferred from the Pokémon Bank or from the Let's Go titles and into Sword or Shield, they can not be moved back to their original destinations.
Pokémon Home also brings the ability to trade with other users at any time. Using the Global Trade System, you can specify a Pokémon you want to trade and which you want to receive, and the service will match you with a Trainer if you both meet the correct criteria for the trade.
You can also create a room and trade Pokémon among friends who are allowed to join, with up to 20 people able to join at once. Additionally, one-on-one trades will be supported with nearby users once you have become friends in the app.
Some features will differ slightly between the smartphone version of Pokémon Home and the Nintendo Switch version. For example, you can only trade Pokémon in the smartphone app, while you can only move Pokémon with Pokémon Sword and Shield in the Switch version.
There will be a free version as well, but its features are limited. The "Basic" plan supports 30 Pokémon for storage, while "Premium" plans support 6,000 Pokémon. For more information on the app, be sure to visit The Pokémon Company's website.