When this feature goes live, a “+” button will appear in private raid lobbies that you’ve joined in person. You can tap the + button to invite up to five friends to join you. Your friends will be notified of raid invitations on their Nearby screen or in push notifications. These invitations will allow your friends to enter the raid lobby, and they will be able to use a pass only when the battle starts.
Next, Pokémon Go will allow you to personalize in-game gifts you send to friends with stickers. When the feature is first introduced players will get a roll of stickers for free, and will have the option of adding a sticker to a gift before sending it to a friend. The website notes, “You can use a sticker only once, so be sure to stock up on more by opening Gifts.” Eventually the stickers will be available to buy, as you’d expect from a free-to-play game.
Source: https://e-cryptonews.com/pokemon-go-raid-invites-will-let-friends-join-your-battle-remotely/