what-say-that "edited"?

Hi.
Can someone tell me what the note: "Edited" means? Times in gray, sometimes colorful and sometimes is gone.

Thanks.

The grey “Edited” indicator reflects a recent Project change, and the text will change to a yellow font if a save action has not been executed in 15 minutes. After 30 minutes, the text will change to red.

A tooltip also indicates when the last save occurred when mouse hovering over the area.

Perfect.
Many Thanks.