Shields in starmade are extremely important. Shields allow your ship to take absorb damage until your shield meter depletes. Adding a shield block to your ship is as simple as placing it on the ship anywhere, but make sure you have sufficient power to run it.
The recharge rate of your shields is very important. A shield recharge rate can be seen on the side of your screen as (number)/s.
Shield recharge is provided by shield-rechargers, which are a separate block to the shield capacitor. Not as a rule, but in general, a high-recharge ship will last longer than a high-capacity ship, due to the cancelling of dps done.
Shield strength can also be seen in build mode on the side of your screen. As with the recharge rate, the more shield block you have on your ship, the stronger the shields.