Microsoft project management software used to plan, manage, and communicate a project schedule and other information among workgroup members, project managers, and other stakeholders.
AFAIK, Microsoft 365 Business Standard includes Microsoft Planner (the standard version) but does not include the paid Microsoft Project plans. Microsoft has rebranded Project under the Planner family, so the advanced Project offerings now appear as Planner Plan 1, Planner and Project Plan 3, and Planner and Project Plan 5. These are separate paid subscriptions.
Planner Plan 1 (formerly Project Plan 1) is $10.00 per user per month with annual commitment. Planner and Project Plan 3 (formerly Project Plan 3) is $30.00 per user per month and includes the Project desktop application and Project Online along with advanced project management features such as baselines, critical path, resource management, and financials. Planner and Project Plan 5 (formerly Project Plan 5) is $55.00 per user per month and adds advanced portfolio and enterprise resource management capabilities.
To add Project capabilities to your existing Microsoft 365 Business Standard subscription, a global or billing administrator purchases the appropriate Planner/Project plan in the Microsoft 365 admin center under Billing and Purchase services. After purchase, the administrator assigns the license only to the specific users who need it. No new tenant is required. Once licensed, users automatically gain access to the additional Planner and Project features, and if licensed for Plan 3 or Plan 5, they can download and install the Project desktop client from the Microsoft 365 portal.
More at https://www.microsoft.com/microsoft-365/business/microsoft-365-business-standard and https://www.microsoft.com/en-us/microsoft-365/planner/microsoft-planner-plans-and-pricing
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hth
Marcin