VMware's Hardware Compatibility List is a database of all of the tested and supported physical hardware. The physical hardware that's chosen to support the created design must be checked against the HCL to ensure that it will be supported. This includes storage devices, I/O devices, and servers. It is important to ensure not only that the hardware vendor and model are supported, but also that the firmware version of the hardware is supported.
Verifying support against the HCL is important not only for new designs, but also when upgrading a design from one version to another in vSphere. Legacy hardware is often removed from the HCL when new versions of vSphere are released.
