Battle Training allows you to practice for Trainer Battles on your own. It is similar to Trainer Battles; however, you battle against a Team Leader (Blanche, Candela, or Spark) instead of other Trainers. You can battle as many times as you want, but you’ll only receive rewards once per day. If you successfully defeat a Team Leader, you’ll also level up your Ace Trainer medal.
To start Battle Training with a Team Leader:
- Open the Nearby screen in the bottom right of the screen in Map View.
- From the Nearby screen, tap on the Battle tab.
- Tap on the image of a Team Leader to start a battle.
Source: Official Pokémon GO support