SharePoint
Microsoft SharePoint is a web-based platform used for sharing files and information. It is designed for teams and provides collaboration features, such as project management, messaging, and shared document storage.
SharePoint is commonly used to create a company intranet, which can only be accessed by employees. It provides a secure platform for team members to exchange files and share information. SharePoint may also be used to create an extranet, as a way for remote clients and business partners to share content securely. Since SharePoint is web-based, users can access the content from a variety of devices using a standard web browser.
SharePoint sites may be hosted by Microsoft using SharePoint Online, or internally using SharePoint Server.
SharePoint Online
SharePoint Online is included with Microsoft Office 365 for Business. It automatically creates a team site when you create an Office Group or Team. You can use the SharePoint web interface to customize the layout of the site, add pages, and share files. Content published using SharePoint Online is hosted in the cloud (on Microsoft's servers) and can be accessed remotely by authorized users.
SharePoint Server
SharePoint Server is a program that runs on a local machine, such as an internal web server, within a corporate network. It provides more control over teams and groups and extra site customization. It may also add extra security if the intranet is hosted behind a local firewall. However, because SharePoint Server is hosted locally, it requires additional hardware, more administration, and manual updates. For this reason, SharePoint Server is most often used for enterprise applications that require greater customization and security.