Battery Share is a relatively new feature from Google. It debuted on the Pixel 5 last year, and it is also here on the Pixel 6 and Pixel 6 Pro this year.
Battery Share will allow you to reverse wireless charge other devices on the back of your Pixel 6. Of course, the most likely scenario for this is to charge your Pixel Buds. Which many got for free when pre-ordering their Pixel 6 smartphone. But you could also use this to charge your friend’s phone if they are running low on juice. Of course, their phone is going to need to support wireless charging.
Keep in mind that wireless charging another device on the back of your Pixel 6 is going to use quite a bit of battery from your phone. It’s really more feasible for Pixel Buds, since that is a much smaller battery and won’t use as much juice from your Pixel 6.