Complex sentence: A "Hello, World!" program is a computer program that outputs or displays "Hello, World!" to a user; a very simple program in most programming languages often used to illustrate the basic syntax of a programming language for a working program.
Split into simpler sentences: A "Hello, World!" program is a computer program that outputs or displays "Hello, World!" to a user. Being a very simple program in most programming languages, it is often used to illustrate the basic syntax of a programming language for a working program.