Team Healers are items introduced in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U that only works in team battles. In normal free-for-all battles, the item is useless. When collected, the Team Healer does absolutely nothing to the collector. However, the player can toss it at their teammate, which recovers that player's health. The more damage the player has taken, the more health recovered. By throwing it at an opponent, it may either damage them or heal them.
A healing item. Hit a teammate with this item in Team Battle to reduce your ally's accumulated damage. You can throw it at an enemy, but the damage inflicted will be minimal, so you're better off using it to help your friends. This item will not react if attacked. Oh, and one more thing--you can't reduce your own damage by tossing the item up and letting it hit you. Sorry.
Super Smash Bros. for Nintendo 3DS / Wii U
Wii Super Smash Bros. Brawl (03/2008) Wii U Super Smash Bros. for Wii U
An item exclusive to team battles. If you throw it at injured teammates, it will reduce the damage they've taken so far. It can be used against your foes as well, dealing a little bit of damage, but it can sometimes heal them too. That's the last thing you want!
This item only appears in Team Battles. Throw it to a teammate to reduce their accumulated damage. Alternatively, you can throw it at an opponent. But since it only does a small amount of damage and there's a chance it'll actually heal them instead, why would you bother doing a thing like that...?