Blue cloud icon: A blue cloud icon next to your OneDrive files or folders indicates that the file is only available online. Online-only files don’t take up space on your computer. You can’t open online-only files when your device isn’t connected to the Internet. Learn more about OneDrive Files On-Demand
Green tick icon: When you open an online-only file, it downloads to your device and becomes a locally available file. You can open a locally available file anytime, even without Internet access. If you need more space, you can change the file back to online only. Just right-click the file and select “Free up space.”
Solid green circle with the white check mark: Files that you mark as "Always keep on this device" have the green circle with the white check mark. These always available files download to your device and take up space, but they’re always there for you even when you’re offline.