What is the meaning and significance of "late days"?

The Today display has a Projects table. This table has a "Late" column.

The help page explains parameter as "number of late days in the project".
How to interpret this?

How do we define a "late day"?

A day that has at least one delayed task?

No of days by which the most critical path is delayed?

(To me, the second definition seems to be more relevant.)

Secondly, how do we define a "delayed" task?

If the resource asks for more time in the Left column?

if the resource fails to complete it in given time, and ALSO fails to ask for more time?

Thirdly, the Projects table is shown to both managers and resources (whoever is given visibility).
But how relevant is it to the non-managers? Why should they see it?
(Will it not demoralize the staff if they see a badly delayed project?)

So, if a resource does not enter his hours against a task for several days, what happens to the project status?

Ideally, ProjeQtor should expect that the data is updated by EOD every day.
If there is no status update by EOD, the next day's status should show that work as "not done".
(This helps create pressure on the resources to update their timesheets regularly.)

Of course, if the resource updates his Timesheet belatedly, the project should revise the status accordingly.
(Such tardy updation is undesirable.)