Protect, Build, Defend.
Each team base starts with an active core, having it makes you capable of respawning each time you die. The enemies can destroy your core by hitting it and making damage to the core until it is destroyed. To avoid this you can build an structure around your core and defend your base standing there. You can also improve the core with perks and upgrades that give regeneration or effects to the near players around, including enemies.
On top of the core there is a health bar, depending on the quality of your weapons you will do more or less damage to the core and having more chances to destroy it after being defeated by the enemies protecting their base.