Reservoirs in hydraulic systems are essentially large containers or tanks that hold hydraulic fluid. They act as storage units, providing a ready supply of hydraulic fluid for the system to use when needed. Think of them like a reservoir of water in a dam: the fluid is stored in the reservoir until it's needed to power the hydraulic machinery. Reservoirs are usually equipped with features like filters to keep the fluid clean, breathers to regulate air pressure, and sight gauges to monitor fluid levels. They play a vital role in hydraulic systems, ensuring there's always enough clean fluid available to keep the machinery running smoothly and efficiently.