A Joomla field group collects custom fields into a meaningful set. It helps organise the content editing form.
Why groups are useful
Fields such as Date, Location and Organiser can form an Event group. Joomla may display them in a separate form area or tab. A group is not a new article type and does not store values instead of the individual fields.
What to check
A group belongs to a component context. Review publication, language and access for both the group and its Joomla fields, then open the target record with the working role. Form organisation and public presentation can be configured independently.
Joomla field groups simplify editorial input. Public output still requires appropriate settings and layouts.