Search Engine Optimisation gets you found in the first place. But social media then tells friends of friends about you, and this can result in far more traffic than SEO alone.
If you use Search Engine Optimisation to target a phrase that has say 100 exact match traffic per month, you could conceivably get say 20 of those clicks. If 5 of those people “like” your page, and they each have 100+ friends, you have then told your story to 500+ people, far more than the monthly traffic for that phrase.
While there are many social media websites, the important ones are Facebook, and Google+
In addition, you need to link to your Google+ page from your site, and in turn link to your website from your Google+ page. This helps Google associate the pages with each other, per Google+ pages:
giving “Google information they can use to determine the relevancy of your site to a user query in Google Web Search. It also makes your site eligible for Google+ Direct Connect.”
Google+ Direct connect is a new search, whereby you can search for [+brand] ie +pepsi, and get a business’s Google+ page.
Code for the various buttons: