Phase Shift (PS) refers to the change in phase of a signal over time, while Phase Shift Keying (PSK) is a specific modulation technique that uses phase shifts to encode data for transmission. PSK adjusts the phase of a signal based on the digital bits being transmitted, such as using a phase of 0 for a bit 0 and 180 degrees for a bit 1. The discussion highlights the need for further reading to understand the relationship between these concepts, with suggestions for introductory resources. Overall, the conversation emphasizes the importance of understanding both terms in the context of communication systems. The user expresses gratitude for the information and indicates their study on the topic is now complete.