Computer languages can be categorized as either low-level or high-level. Low-level languages like machine language and assembly language provide little abstraction from computer hardware and use numeric codes that are directly understandable by computers. High-level languages allow problems to be solved using terminology more familiar to humans and are easier for programmers to use. Examples include C, C++, Java, and JavaScript. Operating systems act as an interface between application software, hardware, and users, performing functions like memory management, task scheduling, and file handling.