Many players won't be aware that Anthem has a combo system. It wasn't detailed in the demo, and there's nothing on the HUD to suggest that your Javelin, when performing X, will result in Y. Despite this, performing combos as a team, and valuing from the increased damage they provide (typically AOE) is invaluable and arguably mandatory at higher difficulty settings.

Chaining abilities together ensures that you and your team will be dealing the highest damage possible, and with many combos providing AOE bonuses, it's often invaluable for quickly clearing wavesand challenging bosses quickly

Primers

Primers are abilities which directly apply an effect to enemies when they're affected by it. Typically, any ability which causes a lingering effect will allow you or your team to then follow up with a Detonator. Each class typically has 3 Primers (with the exception of Storm, whom has 5), that vary across their abilities, gear, melee or Ultimate.

Ranger Primers

• Explosive Blaze (Fire)
• Frost Grenade (Ice)
• Venom Darts (Poison)
• Shock Mace (Lightning)

Colossus Primers

• Firewall Mortar (Fire)
• Flamethrower (Fire)
• Acid Spitter (Poison)

Storm Primers

• Rime Blast (Ice)
• Living Fire (Fire)
• Hoarfrost Shards (Ice)
• Ball Lightning (Lightning)
• Elemental Storm (Fire, Ice and Lightning)

Interceptor Primers

• Acid Bomb (Poison)
• Cyro Claive (Ice)
• Corrosive Spray (Poison)

Detonaters

Detonators are the trigger for Primers and allow each Javelin to consume the primer effect. Based on which Javelin Detonates the Primer, will cause a unique Combo Effect. In a random player setting, it can be difficult to coordinate combos, and have specific Javelin trigger specific combos. However, in a group setting it's imperative to understand which Combo Effect you need, and when.

Ranger Detonators

• Frag Grenade (Grenade)
• Seeking Missile (Assault Launcher Gear) 
• Multi-Target Missile Battery (Ultimate)

Colossus Detonators

• Explosive Mortar (Ordnance Launcher)
• Lightning Coil (Ordnance Launcher)
• Heavy Cannon (Heavy Assault Launcher)
• Railgun (Heavy Assault Launcher)
• Heavy Smash (Melee)
• Siege Cannon (Ultimate)

Storm Detonators

• Lightning Strike (Blast Seal)
• Flaming Orb (Focus Seal)
• Glacial Beam (Focus Seal)
• Fiery Strike (Melee)
• Elemental Storm (Ultimate)

Interceptor Detonators

• Seeker Glaive (Assault System)
• Spark Dash (Assault System)
• Tempest Strike (Strike System)
• Bladed Daggers (Melee)
• Assassin's Blade (Ultimate)

Combo Effects

Ranger: Critical Target Damage - When the Ranger Detonates a Primer, the enemy affected will suffer a high amount of burst damage instantly. 

Colossus: AOE Explosion - Similarly to the Ranger's, a Colossus who Detonates a Primer will cause an AOE explosion, dealing high damage to all those in the target area. 

Storm: AOE Spread - Storm when triggering a combo will spread the elemental effect to all nearby enemies. Your opponent suffering from poison? All those hit by the Detonator will also be infected. 

Interceptor: Aura - With the Interceptor often being in and amongst the enemy, Primers he Detonates will cause all enemies around him to suffer the elemental effect.