A Rack Mounted UPS is a flat, horizontal unit designed to be installed inside a standard 19-inch equipment rack, typically used in data centers to save floor space.

A Tower UPS is a freestanding, vertical unit that resembles a desktop PC and is commonly used in smaller offices or for standalone applications.

A Monolithic UPS is a traditional, single, standalone unit with a fixed capacity and all major subsystems (rectifier, inverter, etc.) integrated into one chassis. It provides robust protection but lacks the flexibility to easily scale power capacity or add internal redundancy without purchasing a completely new system.

A Modular UPS system is built from multiple, independent, and interchangeable power modules housed in a frame, allowing it to easily scale power capacity and build redundancy (N+1) by adding or removing hot-swappable modules. This design provides high availability, reduces mean time to repair, and allows for a "pay-as-you-grow" approach to investment.

A Static Transfer Switch (STS) is an electronic device that uses solid-state components to automatically switch a critical load between two independent AC power sources, typically two UPS units, in milliseconds without interruption.

PDU's (Power Distribution Units) are devices that distribute electrical power to multiple pieces of equipment within a rack or data center, often providing monitoring and management features.