Comments in C++ are used to document code and provide explanations or notes for other programmers who may be reading the code. C++ supports two types of comments:

1. Single-line comments: These comments begin with two forward slashes (//) and continue until the end of the line. Anything on the line after the // is treated as a comment and is ignored by the compiler. For example:

// This is a single-line comment
std::cout << "Hello, World!"; // This line also has a comment

2. Multi-line comments: These comments begin with a forward slash followed by an asterisk (/*) and end with an asterisk followed by a forward slash (*/). Anything between the /* and */ is treated as a comment and is ignored by the compiler. Multi-line comments can span multiple lines. For example:

/* This is a multi-line comment
   that spans multiple lines */
std::cout << "Hello, World!"; /* This line also has a comment */

It's important to use comments judiciously and to keep them up to date as code changes over time. Well-written comments can help make code easier to understand and maintain, while poorly written or out-of-date comments can be misleading and cause confusion.