Ids with respect to client and server access

Hello, when it comes to ids, say an actor has an id of

When I use my web browser client and go to that URL, will I get the JSON object for that actor that includes their inboxes/outboxes or will I see their public facing website?

I am trying to understand when the object json is shown/retrieved and when the html/css version of the client is shown?

Can you sent json object and show html/css at same time? I thought it would need seperate destinations similair to api’s

Also, with create activites, I noticed on the examples on w3 that all create activities had a unique id too. Is this just for records in a database? Or is this id url accessible to?

Thank you for any responses.

The response is based on the Accept header. If a request is sent with Accept: application/activity+json, the server should respond with the activity JSON.

All activities should have unique IDs, but some implementations consider some activities to be private and therefore cannot necessarily be retrieved

Thank would make more sense, thank you.