There are various ways to earn money through the so-called webinars, which are online video courses – you can sell the videos as they are or you can send them free, where you sell a product that you can earn money on.
These small courses may vary from few minutes to several hours and can be presented in a variety of ways – your selling point is to help people and have a product (physical or mental) that can remedy some problems for people or there is a specific subject you know a lot about, so you can teach and share your knowledge.
If you can promote your videos and find your segment, then you have the opportunity for customers. There are many who give their webinars free to the interested, as it can expand their mailing list, or simply because they want to spread useful knowledge.
Others publish their video for free because it promotes a product they sell and are if they are interested in their webinar, there is a good chance that they also may be interested in the product. This allows the free provider of webinars to earn even more money when advertising own products in Webinars.