The following video explains the altitude restrictions and other altitudes published on a STAR, Standard Terminal Arrival Procedures. The following video includes examples of how altitude restrictions apply when you are given the clearance to "Descend Via" a STAR.
The following arrival procedures are mentioned in the video and can be viewed and downloaded by clicking on the image below:
PAWLING TWO ARRIVAL JFK:
PHLBO TWO ARRIVAL EWR: