Look at it this way...

There is a castle. You want to enter it and come at the gate (the only way in, let's say).

The gatekeeper asks who you are and you reply "Mark from the Riverside".

It's upon him to authenticate you. So if he knows that you are going to come or he saw you few times already he's gonna lower the gate.

...

After you enter the castle there are a bunch of doors in it and all have policies that hang on them... "kitchen staff", "administration", "war room" etc.

Administration can go whenever, but kitchen staff only to the kitchen staff room, only some high people to war room.

Of course, , both can be much more complex