Locomotive terminology

The injector is used to replenish the water in the boiler from that stored in the side tank or tender.

Vacuum ejector:
The ejector is used to create a vacuum in the braking system which is used to release the brakes and keep them released.
If the vacuum is broken the brakes come on automatically.

Cylinder drain cocks:
To remove water that may have condensed in the cylinders, drain cocks are opened to allow the water to escape.
This escaping water is accompanied by steam which escapes with the water from the cylinders.