Inbound link building is the most important off-page SEO ranking factor but there are others like web citations that make a difference as well. This article discusses various SEO actions that can be taken on sites someone else controls.
User intent can be described as the actions taken by someone performing a search in Google or Bing based on their intentions. For example, there is a difference in intent between someone who is shopping for a car and someone who is buying a car. Search engines watch every click as well as how long a web searcher stays on a web page. If the web page is of sufficient quality to satisfy the user they will stay on the page. This is considered something like a vote of confidence to search engines that a web page is of high quality relating to the user's intent.
The amount of traffic a web page receives, especially traffic that is considered to successfully fulfill user intent is important. Random traffic, for example, that's generated by web robots developed for that purpose, is of little to no use. In other words, the quality of the traffic is as important as the traffic itself in determining the value of a web page for a given purpose.
The number of incoming links to the target site from other websites is very important. But the quality of the links is important too. A link to a financial services firm from a bakery website is far less important than a link from another financial services company. Link building continues to be one of the most important off-page actions that can affect search engine ranking.