Precision Time Protocol (PTP) is a relatively new protocol that was developed to improve the time synchronization accuracy that is obtainable over a Local Area Network (LAN). Specifications for PTP are defined in the IEEE-1588 standard. In PTP terminology, the Grandmaster is the distributor of accurate time and the Slave is the receiver of this time. The Slave synchronizes itself to the Grandmaster.
The most common network timekeeping protocol is the Network Time Protocol (NTP). In NTP terminology, the Server is the distributor of accurate time and the Client is the receiver of this time. The Client synchronizes itself to the Server.
With NTP you can get client synchronization accuracies in the millisecond range. With PTP you can get slave synchronization accuracies in the nanosecond or microsecond range. Synchronization accuracy depends not just on the PTP Grandmaster, but also on the network topology such as switch and slave hardware.