A syscall, or system call, is a way for programs to request services from the operating system's kernel. It acts as a bridge between user applications and the hardware, allowing software to perform tasks like reading files, creating processes, or communicating over networks. When a program needs to perform a function that requires higher privileges, it uses a syscall to safely interact with the operating system. This ensures that user applications cannot directly access hardware resources, maintaining system stability and security. Common examples of syscalls include open, read, and write.