A blade is literally a self-contained server, which collectively fits into an enclosure with other blades. Sometimes known as a chassis, this enclosure provides the power, cooling, connectivity, and management to each blade. The blade servers themselves contain only the core processing elements, making them hot-swappable. HP refers to the entire package as a BladeSystem.
To get a better idea of what a single blade contains, an HP ProLiant blade holds hot-plug hard-drives, multiple I/O cards, memory, multi-function network interconnects, and Integrated Lights Out remote management. For additional storage, blades can connect to another storage blade or to a network attached SAN.