A class is an event where an instructor actively supports and guides a group of students in building knowledge and skills. The instructor is highly knowledgeable and well-trained in order to effectively help the students in their learning journey.
A workshop is an event where a facilitator guides participants in an activity or project. The facilitator should be able to help and give advice to the participants, but doesn't necessarily have to be a total "expert".
A Hangout is like a casual get-together where friends work on their own stuff while keeping each other company. It's all about hanging out, chatting, and sharing ideas. The person in charge, aka the Host, handles all the arrangements, from setting the time and place to tidying up afterwards.