Dual In-line Memory Modules (DIMMs) are circuit boards that hold memory chips used in computers and servers. They provide a way to increase the amount of Random Access Memory (RAM) available, which helps improve system performance. DIMMs come in various sizes and types, including DDR, DDR2, DDR3, and DDR4, each offering different speeds and power efficiencies. Each DIMM has a 64-bit data width, allowing it to transfer data more efficiently than older memory types. They are designed to fit into specific slots on the motherboard, ensuring compatibility with the system. Proper installation of DIMMs is crucial for optimal performance and stability.