printf is a function in the C programming language that is used to print formatted output to the standard output stream. It stands for "print formatted" and allows developers to output data to the console or terminal in a specified format, such as text, integers, or floating-point numbers. printf takes a format string as its first argument, which contains placeholders for variables and formatting instructions. These placeholders are replaced with the actual values of the variables during runtime. The printf function is widely used in C and other programming languages for debugging, logging, and user interface display purposes.