Google +1 is a service similar to facebook likes. In an attempt to overcome Facebook competition, Google has come out with this option where Google users can give a vote for any page they like on the internet.
If you are logged in while searching, you can see the +1 option along with the search results.
Apart from this, google gives the ability for webmasters to add this code in each of the pages of a website.
For giving a vote to this page, click on
<!-- Place this tag where you want the +1 button to render -->
<g:plusone size="tall" annotation="inline"></g:plusone>
<!-- Place this render call where appropriate -->
<script type="text/javascript">
(function() {
var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
po.src = 'https://apis.google.com/js/plusone.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
})();
</script>
Check http://www.google.com/webmasters/+1/button/ for getting this code in other sizes.
How this will impact your SEO?
Google says “The +1 button lets you start great conversations. When you click +1 you’re publicly recommending pages across the web. You can also use +1 to share with the right circles on Google+. +1’s can help improve Google Search too, since you can see which pages your social connections have +1′d right beneath search results and ads.”