Meta tags are metadata that provide information about a web page, such as keywords and descriptions. They are optional HTML tags that go inside the <head> element and can be used by search engines. There are three main meta tag attributes - name, content, and http-equiv. The name attribute specifies the type of metadata, content provides the value, and http-equiv can refresh the page or set a cookie. Meta tags must be properly closed in XHTML using an end tag.