A webinar is a talk, class, or meeting that happens over the Internet, where one person or a small group presents and many people watch and listen. Usually the audience can send questions by typing, and sometimes they can speak too. Companies use webinars to teach customers about a product; schools and groups use them for training.

The word is a squeeze of 'web' and 'seminar', so the seminar part is important: it is mostly one-way. Someone is teaching or showing something, and the rest are there to learn. That is what makes it different from a normal video meeting, where everyone talks. A meeting with five people talking freely is not a webinar; it is just an online meeting.

The word belongs to business and education. It sounds a bit formal, the kind of thing that appears on a company email or a poster. Friends do not have a webinar together. Note also that it is often free but you must sign up first, and many are recorded so you can watch later.