Language learning platform Duolingo's stock surged more than 35 percent after launching its IPO on the Nasdaq Wednesday. Co-founder and CEO Luis von Ahn joined Cheddar’s Closing Bell to talk about bringing the company to the public market and how his company’s services differ from competitors like Babbel or Rosetta Stone. He noted that the company offers free services creating a big database of users to help improve its teaching tools. "The thing about our company, I think, that has really attracted investors a lot is that our revenues have been growing fast," he said, explaining most of its income came from premium subscribers.