Programmable Logic Devices (PLDs) are electronic components that can be programmed to perform specific logic functions. CPLDs (Complex Programmable Logic Devices) and FPGAs (Field-Programmable Gate Arrays) are two types of PLDs. CPLDs are typically used for smaller, less complex designs, while FPGAs are used for larger, more complex designs. Both CPLDs and FPGAs offer flexibility and reprogrammability, making them ideal for prototyping and implementing digital logic circuits.