GAP is a computer algebra system with a focus on computational group theory.
GAP Days are meetings where developers and users with programming experience are invited to influence the future development of GAP by initiating and contributing to discussions and coding sprints. As enough GAP experts will be around for technical support, the meetings usually offer good opportunities for people to work on their own packages. To streamline each meeting the organizers will usually suggest a few main topics to work on during the week.
The meetings are also suitable for advertising recent developments in core GAP and packages via short talks. However, the focus of the meetings is usually on code development, with talks only playing a minor role.