thanks for sharing very useful information.

Can someone tell me more about:
This means to post article to ehow dot com or write step-by-step article?
Many thanks you.

backlinks are incoming links that obtain your web traffic

You have nicely explained about backlinks and how we can generate it but I do not agree with your one point i.e. buying links. This technique is not considered as a good technique and generally considered as one of the Black hat SEO technique. Google penalize those website which buy backlinks rather than building it manually.

isn't buying links forbidden by google?

create a blog. blogs can get you lot of inbound links to your website.
Create an Rss feed.
create a banners to faciliate links to your web project.
Post good and original content.

Yeah buying links is not really whitehat, more of greyhat but it sometimes works.

Maybe work on article marketing, guest posting and etc...

Submit your site in various website directories
Submit your article in article directory site
Forum posting
Posting classifieds sites
Blog commenting.

Nice information thanks for sharing with us

Forums like this site - siteownersforums.com

Backlinks are important because they are seen as a type of credit given to you from other webmasters. The more quality backlinks the better.

Back links are incoming links to a web page or website. In technical terms it is received by a single web node from another web node.

Replicate competitors' best backlinks. ...
Analyze competitors' mentions. ...
Build backlinks with infographics. ...
Guest blogging. ...