Tier 1 Protoss

Upgrading to Tier 1 will not only increase your bases life, but it will also start spawning different units at a different spawn rate.

Tier 1 Protoss
If you upgrade to Tier 1 Protoss, your base will change into a gateway and you will start spawning prisoner zealots. The spawning rate is roughly 1 every 12 seconds.

An upgrade, often called a racial, for your current spawning unit can be found at your current base. In this case the upgrade is Charge, this allows all your prisoner zealots to quickly approach enemy units within a certain range.

More on Tier 1 Protoss
Tier 1 Protoss upgrades into Tier 2 Protoss at the cost of 1400 minerals.

As with all bases, Tier 1 Protoss can also cast a chronoboost to increase the spawn rate/upgrade rate/attack rate of the base itself or the nearby cannon.