In order to understand the importance of link building, it's important to first understand the basics of how a link is created, how the search engines see links, and what they can interpret from them.
Start of link tag: Called an anchor tag (hence the "a"), this opens the link tag and tells search engines that a link to something else is about to follow.
Link referral location: The "href" stands for "hyperlink referral," and the text inside the quotation marks indicates the URL to which the link is pointing. This doesn't always have to be a web page; it could be the address of an image or a file to download. Occasionally, you'll see something other than a URL, beginning with a # sign. These are local links, which take you to a different section of the page you're already on.
Visible/anchor text of link: This is the little bit of text that users see on the page, and on which they need to click if they want to open the link. The text is usually formatted in some way to make it stand out from the text that surrounds it, often with blue color and/or underlining, signaling to users that it is a clickable link.
Closure of link tag: This signals the end of the link tag to the search engines.
View full article - MOZ Link Building for SEO
