What does the eye symbol mean?

What does the eye symbol mean?

Indicates: watch
Red for: watch failed

You may need to reopen the editor

He means file system watching, in order to maintain synced with outside changes to assets.

there was a problem in my project i update from a old version to the new version.
When i open the editor i get the red eye icon and get a freeze when i tab out.
Found the bug i restart the editor dont tab out and see the error log it say there cant find my script in a node so i delete the empty script in the node and put my old script and now it dont freeze the editor.