Spinners indicate when a user has to wait for something else to occur. They delay showing for 300ms to improve perceived performance.
The label on a spinner is for accessibility. You should pick labels that relate to the specific part of the product it's being used in ("Loading homefeed" for instance).
Component quality checklist
Component is available in Figma across all platforms.
Component is available in code for web and mobile web.
Component is not currently available in code for iOS.
Component is not currently available in code for Android.