Khan Academy is a philanthropically supported education site with a variety of content, such that there is something for anyone between 3 or 4 years old and Betty White. The site came about-like many great things in history - much by accident. Sal Khan was tutoring his niece remotely. Others found his videos and found them useful. Eventually, a decision was made to launch the site.
☀ All Khan Academy content is available for free at: www.khanacademy.org