Tip: when searching the internet for instructional videos add terms such as National Geographic, Crash Course, Khan Academy, BBC Bitesize, BBC, ABC, or CNN in order to access videos from these reputable organizations.
Alternatively, try searching some of the following websites:
There are many educational videos on Youtube and many ways to find them. You can:
search for your topic from the home page, or
browse known sites, for example: "Crash Course", "Ted Talks", "National Geographic", "MinutePhysics", "AsapScience" or "the History channel", or for discipline (or subject) specific videos, for example, Science, Biology, Maths or Algebra.