Comment is non-executable line in source code used to describe a piece of code or program. Comments provides inline documentation of source code and enhances readability of the code. It describes what a piece of code does.
Comment are for readers not for compilers. They make source code more developer friendly.
Single line Comment begin with // double forward slash character. Characters following // is treated as comment and is not executed by the compiler. Single line comments are best suited when you want to add short detail about a complex code that can be described in a line.
Multi-line Comment are used to add a detailed description about the code. It begins with /* character and ends with */. Characters between /* */ are treated as comments.