Schedule 13G is an alternative SEC filing for the 13D which must be filed by anyone who acquires ownership in a public company of more than 5% of the outstanding stock. The 13G filing is considered a more passive version of the 13D and has fewer reporting requirements than the 13D. Activist practices are not permitted by 13G filers unless they refile a 13D. http://en.wikipedia.org/wiki/Schedule_13G