As the number of projects and teams grow, so does the corresponding number of jobs running on Jenkins. Users find that they need to organize their projects and jobs to make management of them easier. Jenkins does not provide built-in functionality that addresses this need.
The Folders plugin allows you to organize jobs into hierarchical folders, much like how you organize files in directories in your file system. This allows you to group related jobs together - you can then group on things like department, projects and jobs in a specific folder. Folders can also define properties that are visible to jobs inside, enabling you to simplify branch and/or workflow management.
Folders allows you to set security permissions (with the Role-based Access Control plugin) on a per folder basis. Roles can be inherited (or filtered out) within the nested folder hierarchy. For example: the engineering department folder can give broad permissions to all engineers, but the project Foo sub-folder only allows certain engineers to modify it.
Folders then allow you to rapidly clone a folder with its children intact. So you can create, for example, a template folder that can be copied and allocated to a new group coming onboard, yet it retains the same folder hierarchy.
Finally, folders are namespace-aware. Therefore, you can have jobs with the same name that sit under different hierarchies.