LINK EXCHANGE(OFF PAGE OPTIMIZATION)

Link Exchange:Link  Exchange is the one of the most best way to get solid back link for the site , actually Link Exchange works when two sites exchange their links between each other, so when Google Crawl any page of that sites , the both site get benefit from this. But only that link exchange will give benefit to the site when both sites are having high/good PR(page rank).
Link exchange happen between two site . this is best way to share your site link to other sites or blog . you can get more visitors from other sites . this is very effective in seo . you can grow your viewer without any hard work . just put other site link and they also put your link in there sites . i think this is good way to promote your site. 

LINK BUILDING(OFF PAGE SEO)

Link Building:Link building is a tactic that increase the number of websites linking to a particular page or domain. Some factors in this approach include:

• What are the unique characteristics of the site(s) linking to the page or domain?
• How many links are pointing to a specific page or a domain from other unique domain.
• How are the links positioned and what text is included in the hyperlink on the page they live on?

Webmaster Manpreet

 A website with a large number of inbound links(Backlinks) to pages can enjoy a boost in rankings when a search engine deems those links as valuable. The value is determined by authority, relevance, popularity, and other ranking mechanisms that make up the algorithms of Google and other search engines.

Why links are important ??
It is not too hard to understand the links are basically used to make more traffic on the website.Link Building is just like a elections in which leader participant they secure more votes from the user side, it is similar in the case of SEO we make the link building or build inbound links or back links to secure the first position on the search engine. Link building is the one of the key to getting traffic on the website.