Comments are notes about the code, they explain the function performed by a specific code.
Comments are extremely important for you and for other people who will use your code. It is a good idea to get used to comment your code as soon as possible. When you will be working on someone else's code, or even your own code after a long time, comments will save your life.
Browsers and servers will ignore comments. In PHP you can use double shash (//) or hash mark (#) syntax for single line comments, slash asterisk (/* … */) syntax for multiline comments.
//this is a single line comment (C++ style)
#this is another way to write a single line comment (Unix shell style)
COMMENT (C style)
Click here to read about how to output data in PHP.