The backlinks are incoming links to your blog.
The google pagerank is the score of your blog.
For a higher pagerank your blog needs to have backlinks. The most important factor isn`t the quantity of backlinks , more important is the pagerank of each backlink. The anchor text is also important, the anchor text is a clickable text ,it`s need to be relevant to your page. As you see in the above picture , the page C has a high pagerank with a single backlink. The page E has a lot of backlinks but with small pageranks. There are 2 type of links: DoFollow and NoFollow links. The NoFollow links have no value in the eyes of search engines, only the DoFollow ones are counted as backlinks.
There are many ways to create backlinks , i will show you some of them: 


1. You can buy the backlinks
There are many backlinks building services, they create backlinks for a fee. This is one of the fastest ways but this isn`t free.2. Comment on other blogs
You can build backlinks by commenting on other blogs. Most blogs have a Name/URL option, put some relevant keywords as name and the adress of your blog as URL or simply leave your link in the text of the comment. Don`t spam , comment something whats relevant to the given post. You can use the Free Fast Blog Finder tool to find high PR blogs.
3. Be active on forums
Most of the forums are allowing signatures , leave your link in your signature. Be active on forums cause every post is a new backlink.
4. Blog directories
Submit your blog to blog directories like DMOZ or Yahoo Directory. You can select from free or payd directories , the result can be the sam at both , but at the paid directories you will be listed more faster.
5. Article Directories
Write quality posts and submit them to article directories like: Ezinearticles and Goarticles

These are the most popular and easiesr ways , but you can find other way too. eg: create a profile on social networks and share your links or use a backlink checker tools to see your competitors backlinks to get ideas.....If you have an idea please feel free to share it in a comment!