According to the "Clash of Clans" wiki, the Barbarian is one of the most important backbones of beginner and intermediate attacks. The Barbarian is a slow unit with low health that attacks with exclusively melee attacks. It makes up for these drawbacks by only taking one supply unit and having the shortest training time and elixir cost of the army units. The Barbarian has no preferred target and will attack the building or enemy nearest to it.
The Barbarian performs one attack per second and at its base level causes eight damage points per hit. As the Barbarian's level increases, it sees significant increases in health and damage dealt, making it a viable unit in armies with Town Hall level eight and above. It's common to use archers and giants to support Barbarians and to compensate for their slow speed and low health.
Because of the Barbarians' high damage and low supply cost, they become an extremely powerful unit when attacking. It doesn't usually work well to deploy Barbarians all at once or in one spot - it's best to deploy Barbarians in small amounts spread out across the map. Barbarians shouldn't be deployed in areas where they will have to break through walls or archer towers because of their slow speed and low health.