Intellectual Property (IP) is defined by the World Office on Intellectual Property (WIPO) as:
"creations of the mind, such as inventions; literary and artistic works; designs; and symbols, names and images used in commerce."
The main protections for IP are copyright (artistic and literary work), trademark (works which distinguish business and goods) and patents (inventions).
Licenses are used to grant authorized use for IP items. For example, whenever you agree to the Terms and Conditions in order to use software or read a website, you are entering into a license agreement. After you agree to the terms, you must abide by them, regardless of other mitigating factors, such as Fair Dealing exemptions.