Overview
Microsoft SharePoint Online provides file storage services for Teams, OneDrive and many other Microsoft services. There are a number of limits with the service and technical information is available here: https://docs.microsoft.com/en-us/office365/servicedescriptions/sharepoint-online-service-description/sharepoint-online-limits
Limits
What is the maximum space available in OneDrive?
For active employees and students, a personal OneDrive site is limited to 100 GB by default.
What is the maximum space available in SharePoint Online sites?
SharePoint Online sites, including SharePoint Storage sites and Teams storage, is limited to 25 TB per site. This is a hard limit although additional sites can be created.
What is the maximum single file size?
A single file cannot be larger than 250 GB.
What is the maximum number of files that can be stored?
There is a limit of 30 million files per site although file counts over 100,000 affect permission management and over 300,000 can affect site performance.
Additional Resources
Microsoft has technical documents on the service limits here: https://docs.microsoft.com/en-us/office365/servicedescriptions/sharepoint-online-service-description/sharepoint-online-limits