This icon indicates a job site with no assets. From left to right they are, a general job site, water loss job site, and mold job site. (There are additional icons available.)

The green plus sign indicates that all the assets have been actively seen by a tracker within the last 24 hours.

A job site typically will be "?" after the first day, unless a tracker in  vehicle sees ALL the assets a job site, because it had to return for one reason or another.