The lead 'stages' can be added/removed or changed here:
The default Leads Stages:
The default Leads Statuses:
To create a new status, click on the Add button and specify the details in a new window:
If the Due value (number of days) is specified and a lead is in this status for more than the specified days, then in the leads list, in the Last activity column (should be enabled), the Status changed output will be highlighted in red color.