There are two types of comments in JavaScript:
1. Single-line comments: These are used for brief explanations or notes. They begin with two forward slashes (//) and extend to the end of the line. Anything written after these slashes on the same line is treated as a comment.
2. Multi-line comments: These are used for longer explanations or to comment out blocks of code. They begin with a forward slash and an asterisk (/*) and end with an asterisk and a forward slash (*/). Everything between these symbols is treated as a comment, regardless of the number of lines.
Using comments effectively helps improve code readability, facilitates collaboration, and aids in debugging or development by allowing you to annotate or temporarily disable code.