# Projects

Projects are the foundation for managing and planning your team's workload.

In the API, each project is a Project object, which is a subclass of [Assignable](/api/resource_management/openapi/assignables). Sub-projects share the same data model and are called [phases](/api/resource_management/openapi/phases). 

> **Note:** Every phase has a parent project; therefore, the `parent_id` for a phase is never `null`. A project's `parent_id` is always `null`.

> **Note:** Other models, such as users, assigned to a project reference that project's `id` value in via their  `assignable_id` property.

> **Note:** You can use the `timeentry_lockout` parameter to control whether a project accepts new time entries. For details, see the `timeentry_lockout` parameter in [Create project](/api/resource_management/openapi/projects/postprojects) or [Update project](/api/resource_management/openapi/projects/putprojectsid).