Niantic has officially confirmed that friends, gifting and trading Pokémon are coming soon to Pokémon GO. When you send a Gift to a friend or participate in a raid or Gym battle with them, you can increase your Friendship Level. As your Friendship Level builds, you’ll then unlock bonuses when you play together. For example, when you and a Great Friend participate in a Gym battle or Raid Battle together, you can earn an Attack bonus to give your Pokémon an edge. You can increase your Friendship Level once per day per friend.
You can also build your Friendship Level by trading Pokémon with a friend. If you’re near a friend and have a Trainer Level of 10 or higher, you can trade Pokémon you’ve caught with that friend. Completing a trade earns a bonus Candy for the Pokémon you’ve traded away, and that bonus can increase if the Pokémon you traded were caught in locations far apart from each other! All trades are powered by Stardust, and some trades require more Stardust than others. As you build your Friendship Level with the friend you are trading with, you’ll find that you can complete the trade with much less Stardust.
Pokémon Blog 
13 thoughts on “First official Pokémon GO screenshots and details for new Friendship Level features, Good Friend, Great Friend, Ultra Friend and Best Friend standings”