Let me break down the revival mechanics for you, since they're quite unique and actually tie into some interesting gameplay dynamics. When someone falls in battle, they become what's called a "broken one" (this creates some really tense moments during missions), and they're basically stuck watching until the team helps them out.

The revival process is actually pretty strategic, because you'll need to grab their head from where they died, and make your way to an extraction point. Here's where it gets interesting - you can't just extract right away, you need to hit your loot quota first (this actually prevents teams from just rushing revivals without completing objectives). When you do manage to bring them back, they start with just 1 hp, which makes them super vulnerable. Getting them to the extraction truck bumps them up to 25 hp, and they'll finally get back to full health when everyone returns to the main ship.

Something worth noting, if you can't get to a teammate's head in time, they'll have to wait for the next mission to rejoin (but there's a neat trick where teammates can share health by standing behind them and holding left mouse button). This whole system really encourages looking out for each other, since losing a teammate can seriously impact your mission success chances.