The Cambrian Period is a geological time frame that lasted from about 541 to 485 million years ago. It marks the beginning of the Paleozoic Era and is known for a significant increase in the diversity of life, often referred to as the "Cambrian Explosion." During this time, many major groups of animals first appeared in the fossil record. The Cambrian Period is characterized by the development of hard-bodied organisms, such as trilobites and early arthropods. The oceans were the primary habitat, and the period saw the emergence of complex ecosystems. This era laid the foundation for future evolutionary developments in marine life.