For search engines that crawl the web, links are the streets between pages. Using sophisticated link analysis, the engines can discover how pages are related to each other and in what ways.

• What is off page SEO?  

          If you optimize content on your website for Google that is considered on page seo.If you do things not on your website (e.g. link building) this is considered off page seo.

• Why Links have so much Importance in SEO ?

          Links to pages on your website from pages on other websites are like popularity votes. The more links a page has the more popular the page becomes but it's not just about the number of links, it's also about the quality of the links. For example if another popular page links to your page the value of that link is higher than a link from a page that isn't popular. It makes sense really and here are some link building techniques

How to get Links to Pages?

• Go to a link seller
  Pros - You will get links, they should make a difference
  Cons - They may be low quality, they may eventually stop working if the link seller is found out, you may have to keep paying to keep them

• Search for links based on merit
  Pros - any links you secure could have a very positive effect on your site, links you secure should last
  Cons - securing links can be very time consuming, time spent looking for links doesn't always bear fruit, you need something worth linking to which also takes time and effort

• Article Marketing and variations on this theme
  Pros - guaranteed keyword rich links, good for generating traffic
  Cons - link quality often low

• Forum spamming and variations on this theme
  Pros - guaranteed links
  Cons - links are low quality, huge numbers of low quality links may give a SPAM signal (this is pure speculation), may harm your company reputation

• Social Media or the leverage engine
  Pros - very effective at securing traffic and links
  Cons - spamming could harm you, creating something that sparks interest isn't easy