A «Hello, World!» program is a computer program that outputs or displays «Hello, World!» to the 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. It is often the very first program people write when they are new to the language.
A «Hello, world!» program is often used to introduce beginning programmers to a programming language. In general, it is simple enough to be understood easily, especially with the guidance of a teacher or a written guide.
In addition, «Hello world!» can be a useful sanity test to make sure that a language’s compiler, development environment, and run-time environment are correctly installed. Configuring a complete programming toolchain from scratch to the point where even trivial programs can be compiled and run can involve substantial amounts of work. For this reason, a simple program is used first when testing a new tool chain.
Source: «Hello, World!» program – Wikipedia