Backlinks are meant to link to your website directly from other websites. For example, if I give my website a link on a football player's photo. When you click the footballer's picture, It will direct you another website. In this example I gave a link for football. Search engines will place a higher value on your website if there are backlinks coming from websites that have content related to the content on your website. Backlinks from websites that have high page ranks will by association help in raising the page rank of your website.
So what does a backlink actually do ?
Backlinks help in getting a higher rank on search engine results pages. It can also help to raise your page rank value. If you want to be on the top with certain words in search engines, you could try to increase the quantity of backlinks from relevant websites. Search engines see the websites which have added your web site and raise your position on search engine results pages.
How can I find the enough Backlink ?
It isn't always possible to get the backlinks that you always want. Link exchanging or building with other websites is a useful way to get backlinks. You can exchange links in 2 ways. Correlative link change and cross link change. Correlative link change’s mean that two web site gives links to one another. Google's algorithm can determine arranged link changes and doesn't penalize websites that do this. Don’t forget that the web sites which you get and give links should be as valuable as your website.