A keyword is a reserved word. You cannot use it as a variable name, constant name etc.
In C# keywords cannot be used as identifiers. However, if we want to use the keywords as identifiers, we may prefix the keyword with @ character.
A list of Reserved Keywords available in C# programming language is given below:
Some identifiers which have special meaning in context of code are called as Contextual Keywords.
A list of Contextual Keywords available in C# programming language is given below: