yep,, two part of linkbuilding was on-page and the other one was off-page,,, on page linkbuilding was the easier one, because you are working on the page itself,,,
Link building is strategy for creating inbound links ones own websites its can be done by being listed in ezine and also many other websites. If you work in Link building so you get more benefits with your websites like increase back link and also ranking in Google and other search engine.
It's the other important half of SEO. Off page optimization like backlinks is an equally important aspect of your SEO work.
It is just part of SEO process. Link building is not everything. There are lot more things in SEO. Forum posting is very important one
link building is a way to promote your website and spreading your website's link on to the internet... it drives the good traffic and good search engine visibility as well..
link building is one of the major factors of off-page seo optimization, more link building efforts helps achieving backlinks and eventually jump up the rankings in search engines.
Actually Google want's link building to happen naturally by others. You can create link bait/hooks so others get hooked to it. As it carries a lot of weight and webmasters can get some direct traffics as well, they always striving to build links as much as possible.