Drupal Group Module

I need to...	Guide	Summary
Understand how Group 3.x is structured	Core Architecture	Read this when you need to understand Group 3.x's data model and how it differs from earlier versions before writing any code.
Know which entity types Group provides	Entity Types	Reference this when you need to know the exact entity type IDs, base tables, bundle systems, and key fields of every entity Group provides.
Create a custom relation type plugin	Plugin System	Read this when creating a custom group relation type plugin to allow a new entity type (or bundle) to be added to groups.
Understand how permissions work	Permissions System	Read this when you need to define custom group permissions, understand the scope system, or programmatically grant/check permissions.
Control access to grouped content	Access Control	Read this when diagnosing access issues, understanding the "explicit forbid" pattern, or writing custom access control for group-related entities.
Write YAML config for group types / roles	Configuration	Reference this when writing or exporting configuration YAML for group types, group roles, relationship types, or plugin config.
Use the Group PHP API programmatically	PHP API	Reference this when writing PHP code to create groups, add members, relate content, or query group data programmatically.
Build Views with Group data	Views Integration	Reference this when building Views that display groups, group members, or content within groups.
Hook into Group with custom code	Hooks and Events	Reference this when looking for extension points to react to Group events without altering core Group logic.
Add nodes to groups (gnode sub-module)	Sub-modules	Reference this when enabling node support, revision support for grouped entities, or looking at how official sub-modules structure their plugins.
Automate group operations with VBO or ECA	Group Actions (contrib)	Read this when you need to automate group operations — adding/removing members or content — via Views Bulk Operations (VBO), ECA workflows, or any Drupal action-based system.
Understand how caching works	Caching	Read this when debugging stale cached output for group-aware content, or when optimizing the performance of group membership and permission lookups.
Compare Group vs Domain vs Permissions by Term	When to Use Group	Read this before starting a project to choose the right access control approach. Picking the wrong module early is expensive to change.
Migrate from v1/v2 to v3	Migration from v1/v2	Read this if you are moving an existing Group 1.x or 2.x site to Group 3.x.
Avoid common mistakes	Common Mistakes	Review this before shipping group-related code to catch frequent errors.
Review security considerations	Security	Review this before deploying a Group-based site to production to understand the trust model and potential vulnerabilities.