Basically, she's sold shitloads of singles in America and now has gold and platinum song certifications totalling over 100m.
"Gold & Platinum is the industry's premier way to celebrate achievement in the marketplace," said your good friend and ours Cary Sherman, who as you well know is Chairman & CEO of RIAA.
"We've given awards to artists for nearly 60 years, but it's rare that we have the opportunity to recognize [she means 'recognise'] a milestone like the one Rihanna has reached. Congratulations to Rihanna! She has not only surpassed RIAA's one-hundred million mark, but also is the first artist to do so. It's an historic feat and a testament to an extraordinary career."
This being Rihanna she was keen to draw attention to it via Instagram, posting this handy chart of how much more she's sold than anyone else (good to see Flo Rida on there though):