Google have several search algorithms to rank a page. Outbound links and ranking factors are most important. Google uses various ranking factors with on-site and off-site SEO methods. Now a day, it is very difficult to rank a site in Google. Even Bing and Yahoo also measure the site rank by various ranking factors.
Google search algorithms: Google panda, Google penguin, Google hummingbird.
Outbound links / External links
Outbound links are usually external links that is link which opens another links through the website
The source link domain name is must to be different from the destination link.
Example: www.esearchadvisors.com contains several posts about Search Engine Optimization Tutorials. Some post linked with the Wikipedia sites for reference. In this scenario, the Wikipedia .org link is the outbound link of esearchadvisors.com
Wikipedia is the top ranking site so the esearchadvisors.com website will get more ranking signals in the concept of outbound links/external links.
Outbound links are also called as backlinks.
Outbound links and ranking factors
Backlinks are the links which pointing your website from other website domains. More number of backlinks helps to increase the site rank in SERP (Search Engine Results Page).
Relevant backlinks are important than normal backlinks. Relevant bank links points other domains having same niche topic/content.
Link relevant can be measured by using contents on the site and how the wordings are match with other domain.