A Radio Net is a gathering on the radio band for licensed amateurs, through you are welcome to just listen in too. The Net controller will announce the basic rules of the net and ask people to call in with their callsign to register before the actual chat starts. Each member is called and can talk for a few minutes, before replies are invited. Then they should not transmit unless requetsed to by the controller or another member. The chats are generally themed around radio subjects as they progress and may include notes of club meetings, but are generally informal affairs.
They can have upto around 20 members and go on for a couple of hours and HF ones cover most of the UK depending on conditions. 2b and 70cm one are usually people in a 20-50 mile radius and you can participate on a hand-held radio if you are prepared to accept that not all members will hear you. They are very welcoming for beginners so don’t be nervous as they do understand and will support you.
https://www.netfinder.radio/nets/country/united-kingdom