This survey provides a thorough analysis of memory mechanisms essential for LLM-based agents, discussing their evolution and application across interoperable environments: - Defines the importance and functionality of memory in agents - Extensive review of current designs and evaluations of memory modules - Highlights applications where memory plays a pivotal role and suggests future directions - Analyzes barriers and offers solutions to enhance agent adaptability and efficacy Implications and Importance: Sets the stage for advanced development in LLM-based agents, fostering avenues for more dynamic and accurate agent-environment interactions. This can greatly inform future research and development in AI deployment in complex systems.