Modding is a slang expression that is derived from the verb modify. When the software license says that it is for a specific person, then it is not legal for that software to be used by some other person on that same computer, even a member of the same family, or another employee of the same company.
Modding refers to the act of modifying a piece of hardware or software or anything else for that matter, to perform a function not originally conceived or intended by the designer. The term modding is often used within the computer game community, particularly in regard to creating new or altered content and sharing that via the web.
It may also be applied to the overclocking of computers in order to increase the frequency at the which the CPU operates. Case modding is also a popular activity amongst many computer enthusiasts which involves the customization of a computer chassis or the installation of water cooling technology.
In connection with automobiles, modding often refers to engine tuning, remapping of a vehicles engine control unit or customization of the bodywork. Computer systems, hardware, and software are often sold or licensed to one home machine, to a business that has many computers, a government agency, or a non-profit organization.