How to alert the squad to an event in Freeplay

Each Primer ability usually inflicts a negative status effect to an enemy or group of enemies, such as ice (slow/freeze) or acid (DoT). Once an enemy has a Primer ability applied to them, the next Detonator ability that hits that enemy will execute the detonating Javelin's combo effect. This will not stop the status effect from the Primer ability. In order to detonate another combo on that same enemy, the enemy will need to be hit with another Primer ability, even if they are still under the status effect from the previous Primer ability.

Some Primer abilities take time before the enemy becomes detonatable. There is an icon that appears over each enemy when they are Primed and ready for detonation. The icon is a small hexagon that depends on the elemental type of the Primer Ability: Ice, Fire, Acid, or Lightning.

In the UI, Primer abilities are marked in the Forge customization window with a circle icon, and Detonator abilities are marked with a star.

Some abilities are neither Primers, nor Detonators, and some abilities (Elemental Storm) are both.

Javelin Combo Effects

• Ranger -- Critical Target Damage: Detonating an enemy causes more damage than any other Javelin's detonation
• Colossus -- Explosion: Detonating an enemy causes an explosion which damages all nearby enemies
• Storm -- Spread: Detonating an enemy causes an explosion which spreads the enemy's elemental status effect to nearby foes
• Interceptor -- Aura: Detonating an enemy causes its elemental status effect to become imbued into your Javelin, which can then be spread to nearby targets through proximity

This info was summarized from Gamespot.

According to the EA website:

The playstyle medal you get at the End of Expedition (EoE) shows you which Legionnaire’s Feats you scored highest on for that Expedition. Once your XP and playstyle medal are awarded, your Feats reset to zero so you’re ready for your next Expedition.

Feats

Feats are small challenges, in five categories, each with bronze, silver, and gold levels.

When you’re out in the world, track your Feats in the Journal section of the Cortex.

Most of the Feat categories are inspired by Legion of Dawn Legionnaires:

• General - Let’s start with the exception. General Feats aren’t associated with a Legionnaire, but they grant you XP for finishing a Mission, reinforcing others, and completing a Stronghold or World Event.
• Artinia - Rewards you for weapon use, defeating elite enemies, and hitting weak points (Soldier medal).
• Cariff - Rewards you for using combos, gear, and multi-kills (Artillery medal).
• Gawnes - Rewards you for using Melee, Ultimate abilities, and defeating Legendary enemies (Executioner medal).
• Yvenia - Rewards you for collecting and harvesting items and repairing the Javelins of downed allies (Sage medal).

Source: https://answers.ea.com/t5/General-Discussion/What-does-the-play-style-medals-mean/td-p/7496266

Players have also found a General Tarsis medal, which appears to be from doing all the Feats at gold level.