IOBrowser is a macOS application for browsing the IOKit registry.
The I/O Registry is a dynamic database that describes a collection of "live" objects (nubs or drivers) and tracks the provider-client relationships between them. When hardware is added or removed from the system, the Registry is immediately updated to reflect the new configuration of devices. A dynamic part of the I/O Kit, the Registry is not stored on disk or archived between boots. Instead, it is built at each system boot and resides in memory.