Memset is a standard library function in the C programming language used to set a block of memory to a specific value. It takes three parameters: a pointer to the memory block, the value to set, and the number of bytes to fill. This function is commonly used to initialize arrays or structures to a known state, improving code reliability and performance. Using memset can help prevent issues related to uninitialized memory, which can lead to unpredictable behavior in programs. It is particularly useful in scenarios where large amounts of memory need to be cleared or initialized quickly, such as in data structures or buffer management.