In C++, a token is the smallest unit of a program that the compiler can understand. Tokens are the building blocks of C++ code and are used to create statements, expressions, and other elements of the language.

There are several types of tokens in C++, including:

1. Keywords: These are reserved words that have a specific meaning in the C++ language, such as “if,” “else,” “for,” “while,” and “class.” Keywords cannot be used as identifiers (variable names or function names).
2. Identifiers: These are names given to various entities in the program, such as variables, functions, classes, or labels. An identifier can consist of letters, digits, and underscore (_) character, but it must start with a letter or an underscore.
3. Constants: These are fixed values that do not change during the execution of the program. Examples include integer constants (e.g., 10, -5), floating-point constants (e.g., 3.14, -0.75), character constants (e.g., ‘a’, ‘5’), and string constants (e.g., “Hello, world!”).
4. Operators: These are symbols that perform specific operations on one or more operands. Examples include arithmetic operators (+, -, *, /), assignment operators (=, +=, -=), comparison operators (==, !=, <, >), and logical operators (&&, ||, !).
5. Delimiters: These are symbols used to separate or group different parts of the program. Common delimiters in C++ include parentheses (), braces {}, brackets [], commas (,), semicolons (;), and colons (:).
6. Special symbols: These are symbols with a specific meaning in C++, such as the dot (.) used for member access, the arrow (->) used for member access through pointers, and the scope resolution operator (::) used to access members of a namespace or class.

The C++ compiler analyzes the source code by breaking it down into tokens and then processes these tokens according to the rules of the language. Understanding the different types of tokens is essential for writing correct and meaningful C++ programs.