In abstract terms, automation saves time, improves productivity, and reduces risk. In specific terms, automation replaces physical/mental labor and skill using powerful technologies that start working independently and keep working reliably.
In psychological terms, automation involves the release of some or all human attention from a certain task with the confidence that the system will handle the rest of the work.
In engineering terms, automation is the design of a system that performs work in response to a trigger state without human initiation, attention, or intervention; where work is any useful combination of physical movements, energy transformations, and information processing.
A chair does not perform any work but it does release attention from the act of sitting, where confidence is proportional to the perceived strength of the chair frame.
A calculator performs math calculations with amazing speed but it does not release attention from the act of solving the math problem, during which the calculator is purely employed to save calculation time.
A gravity-assisted water feeder automatically maintains a certain water height for animals to drink from comfortably. It has a larger refill volume and runs over a longer period of unattended operation than with a simple container. The feeder structure provides the right shape for the water to move and balance itself between the reservoir and the tray, under gravity and a fluctuating pressure differential. The feeder operates passively without energized devices but work is still done within the system.
An industrial CNC waterjet machine performs metal cutting operations with great accuracy, speed, cleanliness, and thermal consistency. While the cutting is done independently by the machine, the activity is still monitored by the operator, so attention is only partially released. The material is mounted and locked on the machine manually-physically; the design is imported and configured into the machine manually-digitally. The machine automates the cutting task as a single step of the larger process which includes client communication, design review, order confirmation, customized production, product finishing, and shipping.