The goal of fezda.com is to offer educational content and tools to facilitate learning.
One of the best ways to internalize a skill is to apply it in a project that you are working on. Example projects are provided, though of course you can use these skills for your own projects.
Some topics have quizzes, allowing you to test and review your skills; the same problem is often presented with different values, and their multiple choice position is scrambled so that the answers can't simply be memorized, allowing you a new challenge each time.
Tools are provided to let you interact with concepts, or to perform simple calculations to use as you learn more advanced skills.