Simplify the following text for a Grade 12 native English-speaking person.
Original: The National Wildlife Federation ( NWF ) is the United States ' largest private , nonprofit conservation education and advocacy organization , with over four million members and supporters , and 47 state and territorial affiliated organizations .
Simplified: The National Wildlife Federation ( NWF ) is the United States ' largest private , nonprofit conservation education and advocacy organization . It has over four million members and supporters .