Whereas older versions of the Microsoft Office suite are deployed as a Windows Installer package, newer versions of Office Professional (starting with the 2019 version) and all versions of Office 365 ProPlus are packaged with Click-to-Run (C2R) technology.
Visio and Project are not included with Office 365 ProPlus. These products are available separately for purchase.
Click-to-Run installations are primarily designed to use the Microsoft Content Delivery Network to stream the installation media to endpoints. C2R deployments can also be configured to cache content on a local network share to minimize internet bandwidth for clients.
Microsoft uses a distributed CDN to deliver content and updates for Office 365 ProPlus. Individual clients typically need access to the CDN to install the Office 365 ProPlus software, obtain updates, and download shared files (such as icons and images) for the Office 365 service. Depending on your organization's requirements, you can configure local servers to host the Office 365 ProPlus content updates.
Part of deploying Office 365 ProPlus is determining which update cadence (referred to as a channel) you will be deploying to users, as you'll see in the next section.