It might be a video of a teacher speaking to the camera, photographs and text about the topic or some mixture of these.
Animated video lessons, in particular, use engaging visuals and simplified explanations to help break down complex topics, making them especially effective in subjects like Science or Math.
[1] The Khan Academy has been successful in teaching mathematics using notes written using Yahoo!
Such lectures are a key part of flip teaching in which the initial work of communicating the essentials of the topic is done by the video lesson.
Another meta-study [6] investigated more than 100 studies and find out that about 75% of the time, students learned better from the video.