Ohai detects data about your operating system. It can be used standalone, but it's primary purpose is to provide node data to Chef.
Ohai will print out a JSON data blob for all the known data about your system. When used with Chef, that data is reported back via node attributes.
This section of the Wiki describes using ohai and writing plugins for it.
Use Patent Claims
These details are provided for information only. No information here is legal advice and should not be used as such.