What is Schedule 13G?

Legal Definition
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.

The security holder of more than 5% but less than 10% must file within 45 days after the end of the calendar year in which the Exchange Act registration becomes effective. If the security holder holds more than 10%, then the holder must file within 10 business days once the threshold is met.
-- Wikipedia