Much like the Facebook Like button, the +1 button or Plus One is a button that is inserted into your site and people who have a profile account can vote on your site as interesting. The button can be placed in any area of the site, the exact location depends basically on the site owner putting the html code in the appropriate location.
The idea behind the button is to try to capture and convert the power of social sharing into a gauge for good websites, acting as another indicator for Google.
How does Google Plus One +1 affect search results?
When a person votes on a site by clicking on the +1, it's indicating to google that that content is relevant, or the website is relevant, search or even advertisement. People who have a relationship with the user of the site that you voted for will receive a small indication when they visit the voted pages of their acquaintances who found that interesting / relevant page and that they trust it. By adding a +1 +1 Plus One button on your site you allow users of your site to recommend it to others.
When a person who owns a Google account and is connected to it performs a search, the results submitted to it can be displayed with the name and indication of people that this user has contact and who marked the pages +1, but if None known has marked any page with +1, you can only display the options with the +1 totals that these pages have already received.
How can the Google Plus One +1 button change my traffic?
Adding the +1 Button on your site allows you to add custom annotations close to your page in search results that can make your snippet more attractive and increase the visibility of your site, increasing the chances of a user visiting your page.
How do I add the +1 +1 Plus button to my site?
Here's how (http://www.google.com/webmasters/+1/button/index.html) to add Google Plusone button on this page, which allows you to choose from 4 button sizes.
After obtaining the code request by email or help desk sending the codes obtained to add Google Plus +