Where are passwords stored for Power Query database connections?

Help me understand where passwords are stored for data connections and how they are accessed.

I've created a couple of spreadsheets with queries connected to network SQL databases.  Subsequently, sometimes when I open a new blank spreadsheet and create a new query to the same databases I don't have to enter the password.  How/where is Power Query accessing that password from?

We continue to have data connection permission issues when I share spreadsheets with other users on the same network.  Sometimes, other users can enter connection details once similar to when I created the query and everything is fine and sometimes they have to enter it every time they open/Refresh All the query.  I'm thinking that if I better understand where those connection details are stored and how they are accessed I can troubleshoot the sporadic connection issues.