Support

From TF2 Wiki

Support classes are the backbone of any team. They give the offensive and defensive classes an extra edge in battle, which can turn the tide of the game in a second. Whether crippling the enemy advance from behind or keeping teammates healed, the support classes are always handy to have around. Medics have the power to heal teammates' heaths and overheal them to 150% of their maximum health. Snipers can take out threats from a distance. Spies can infiltrate behind enemy lines, disable buildings, and assassinate critical threats.