Frame-Relay Traffic Shaping (FRTS) can be hard to understand.
Traffic shaping vs policing
The most important difference between these two is the fact that shaping is designed to delay excess traffic, whereas policing drops the excess traffic.
Shaping uses credits. Before a packet can be sent, the amount of credits equaling the packet size in bits have to be available. Policing is not designed to guarantee bandwidth, it’s designed to limit bandwidth.