C is a a general-purpose, structured, compiled, low-level programming language originally developed by by Dennis Ritchie between 1969 and 1973 at Bell Labs. Dennis Ritchie is to the right in the photo below with Kem Thompson. Thompson also worked at Bell Labs where he designed and implemented the original Unix operating system as well as the B programming language, the the direct predecessor to C.
Due to its low-level nature, C is a very popular language to create operating systems, application software, embedded systems. It has become one of the most commonly used programming languages of all time with use on a very wide range of platforms, e.g. microcontrollers, personal computers, supercomputers, etc.