A comment is a line in your codebase which the compiler ignores, however it can be read by programmers.
Here is a single line comment:
// This is a comment and is ignored
// is used to tell the compiler to ignore the rest of the line.
Noir doesn't have multi-line comments, but you can emulate them via using
// on each line
// This is a multi line
// comment, that is ignored by
// the compiler