Free online learning sites/app
Khan Academy
Site: https://www.khanacademy.org/
Google play store: https://play.google.com/store/apps/details?id=org.khanacademy.android
Khan Academy is an American non-profit educational organization created in 2005 by Sal Khan. Its goal is creating a set of online tools that help educate students. The organization produces short lessons in the form of videos. Its website also includes supplementary practice exercises and materials for educators. All resources are available for free to users of the website and application.
edX
Site: https://www.edx.org/
Google play store: https://play.google.com/store/apps/details?id=org.edx.mobile
edX | Free Online Courses by Harvard, MIT...
edX is an American massive open online course (MOOC) provider created by Harvard and MIT. It hosts online university-level courses in a wide range of disciplines to a worldwide student body, including some courses at no charge.
Coursera
Site: https://www.coursera.org/
Google play store: https://play.google.com/store/apps/details?id=org.coursera.android
Coursera Inc. is an American massive open online course provider founded in 2012 by Stanford University computer science professors Andrew Ng and Daphne Koller. Coursera works with universities and other organizations to offer online courses, certifications, and degrees in a variety of subjects. In 2021 it was estimated that about 150 universities offered more than 4,000 courses through Coursera.