a contract, and like any contract may or may not be upheld in court if it comes to that

a contract between a company or developer and a user that sets forth the terms under which the user acquires a license to use the program

a legal agreement between the software maker and the software user

a legal contract between the manufacturer and/or the author and the end user of an application

an End-User Licensing Agreement -- in other words, a license

End User Licence Agreement The agreement terms for use of the software

End-User License Agreement

End User Licensing Agreement. A provider's legal terms. You, as the "end user," may be required to "click" to accept before you can download software.

The most common type of license, a EULA provides stipulations over how a piece of software may be used within an organization. Some software may be installed on multiple machines so long as only one is running at a time, while other software may only be loaded on one machine ever. In general you cannot have multiple copies of the software running at the same time under a EULA license. Most shrink-wrapped licenses are of this type. Source: TechSoup.org