Everyone can stop answering the obvious lol. How many times can you give the same answer in different ways?
Here is some thing a little more helpful.
Now that everyone has clarified the technical term of a backlink, lets talk about what some actually are.
Web 2.0's - Google "list of web 2.0's". Build little sites on places like wix, weebly, jimdo, and etc... Add 5 pieces of unique content (at least) all backlinked to your site with diversified links.
Wikis - Just f look for places to submit content to wiki sites. (Not wikipedia)
Social Networks - Every share or like you give is a backlink to either your site or your profile.
Become a reputable member of various forums and use signatures.
Buy valuable, high quality back links on high PR niche relevant pages. (dont by pages with PR0 because the site is a PR9, the PR9 domain doesn't help the PR0 page until there is some link juice flowing, iusually use these in my second tier and blast them with whatever on the 3rd)
These are enough for your first tier.
Then you want to give the profiles, web 2.0s and wikis link juice by backlinking them. You can outsource these backlinks but learn how to monitor and be able to determine if a backlink breaks or not. That way if you cant remove the bad/broken link you can alway remove the profile/wiki/web 2.0 that it's pointing to.
You can continue doing this for multiple tiers.
You just have to make sure that the first tier is manual because if something goes wrong you want to be able to have full control of what is pointing at your money site.