What is the difference between a reserved keyword and a contextual keyword in C#?

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After reading https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/ despite the document listing a list of Reserved keywords and a list of Contextual keywords, as well stating how any new keyword added to the C# language will be a contextual keyword... it mentions only "one" difference between Reserved Keywords and Contextual keywords in C#.

Being that a Reserved keyword (e.g. `namespace`, `class`, `int`, `static`, `using`, etc..) cannot be used as an identifier (e.g. namespace identifier, type identifier, type member identifier, etc..) unless it is prefixed with `@`. For example:

namespace @namespace
{
    public class @class
    {
        public int @int = 4;
    }
}

While a Contextual keyword (e.g. `global`, `add`, `var`, `await` etc...) can be used as an identifier (e.g. namespace identifier, type identifier, type member identifier, etc..) without the need to utilize any special character, before a contextual keyword, to do so. For example:

namespace global
{
    public class add
    {
        public int var = 4;
    }
}

Is that really the only difference between a Reserved keyword and a Contextual keyword in C#? Perhaps there is more to it than that in terms of why the above rule exists?

What I have tried:

C# language question concerning C# keywords (reserved and contextual). There is no specific online resource that answer the above question.