A meta-tag is an HTML tag that gives information about the content of a web page, such as what HTML specifications a web page follows or description of a web page's content. A meta-tag does not affect how a web page is displayed on a browser. For online marketing, the most common uses for meta-tags are the keyword, description, and robots exclusion attributes. In fact, only some major search engines use meta-tag content for relevancy.
Some search engines use meta-tag content when they display the results of a search query.
These tags are used to assign a title to the page. In many search engines, this is what the prospective visitor will see in the results, followed by the description. This tag is quickly becoming obsolete. It's purpose is to tell the visiting browser what course of action to take when it visits this page. This is useful if you are not using a standard character set.