The following figure shows a single handle and protocol from the handle database produced by a UEFI driver. The protocol is composed of a GUID and a protocol interface structure.
Many times, the UEFI driver that produces a protocol interface maintains additional private data fields. The protocol interface structure itself simply contains pointers to the protocol function. The protocol functions are actually contained within the UEFI driver. A UEFI driver may produce one protocol or many protocols depending on the driver's complexity.