I'll be more specific, but may use terms you are unfamiliar with:

There are 3 classes, and each class has 2 abilities. The more supporty ones are:

Warlock Healing Rift - Heals players

Warlock Empowering (Damage) Rift - Gives players more damage

Titan Barricade - Covers your whole body

Titan Rally Barricade - Chest high barricade, but instantly reloads weapons when you get behind it

In addition, each class has "Supers" or Ultimates; those beneficial to the team are:

Warlock Well of Radiance - Combination of Healing and Empowering Rift, more powerful, much larger

Hunter Shadow Shot - Tethers all enemies to a single point, spreads damage to all enemies chained, may allow crit damage

Titans also have a melee ability that increases damage done to enemies they hit.