What does 2 threads per core mean?

Could you elaborate on what "2 threads per core" signifies in the context of computer processors? Specifically, I'm curious about how this relates to the overall performance and efficiency of a system. Is it a feature that allows for faster processing? Does it improve multitasking capabilities? And how does it differ from a traditional single-threaded core design? Your expertise in this area would be invaluable in clarifying these questions and providing a comprehensive understanding of the concept.