Spear-phishing is a technique. One of the ways someone can take advantage of your computer, your network, and the information that it contains is to send you an e-mail that looks like a legitimate e-mail, which would have an attachment that would look very attractive to you or be of interest to you. By clicking on this attachment you would get a document pulled up. To the user there's no apparent change, but in the background there would be some things happening to install something on your computer that could be used later to steal or extract information from your computer network.
On April 3rd, 2012. See this statement in context.