What exactly should I put in these registered application settings fields?

Question

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Code example:

namespace Program
{
 \\...
}

Here are the settings fields: https://photos.app.goo.gl/nXKXdDF49vWNmkQd9
In the "Namespace" you need to insert the name namespace, that is, "Program" (writes that CAPITAL letters are not allowed), and in the "Application Domain" AppDomain. FriendlyName(it gives an error that top-level domains are not allowed)? What exactly is meant by "Namespace" and "Application Domain" here? Please provide examples of what needs to be included here.