A sprint is an open session where attendees can work on a specific open source project with the guidance of a core contributor. Walk-ins after the session has started are welcome!
Sprints are an excellent opportunity to make your first contribution to an open source project in a friendly, guided environment. They are also an excellent opportunity to meet the maintainers of the tools you use.
You do not need specific experience or context before coming to a sprint. Projects will have a list of bite-sized issues looking for someone (you!) to fix them! Just bring your laptop!