Undercounter units are built to fit below a standard kitchen counter, typically around 850 mm high. They come with doors or drawers and are usually front-breathing, meaning they take in and push out air through a grille at the front rather than the back or sides. That matters because a unit tucked under a counter has no space behind it for hot air to escape.
The idea is to keep ingredients exactly where they are used. A tandoor station may keep marinated tikka and dough below the counter; a bar may keep juices, garnishes and syrups; a café may keep milk under the espresso machine. Cooks reach down instead of walking to a reach-in across the kitchen, which saves time and cuts door openings on the main storage unit.
Capacity is limited compared with an upright, so undercounters are best treated as working storage that is restocked from a reach-in or cold room before each service. Many models double as a worktop, chef base or prep table depending on what sits on top of them.