O365 AD and Windows Azure AD - whats the relation?

I am very, very new to the world of web app development.

This is what I was doing today and have a few questions:

1. Got a trial subscription to Azure and added a domain onAzure.onmicrosoft.com
2. Followed msdn.microsoft.com/en-us/library/windowsazure/dn151791.aspx and was able to query the list of users on the Azure AD by following the exercise in "Using the Graph API to...."
3. What I did next was that I simply moved the following from my ASP.Net app to a console app's config file and was still able to get the list of users. Of course, I used the Graph API Helper and got the tenantName i.e. the Guid by stepping into code.

string tenantName = ConfigurationManager.AppSettings["Tenant"];
string clientId = ConfigurationManager.AppSettings["ClientId"];
string password = ConfigurationManager.AppSettings["Password"];

That was about Azure AD.

Now, I also got an O365 trial subscription and have onOffice.onmicrosoft.com. I have a few users here as well.

How do I get the list of users I created for onOffice.onmicrosoft.com in my console app? Is there an easier way? Let us assume I need to run it as a windows service and keep some local table/ text file in sync with the users that are being created and deleted on O365.

Essentially, is there a way to generate the client id and password like the Azure Portal did for me?

If yes, how do I grab the tenant id?

I know O365 too uses Azure AD but my Azure tenant is different than my O365 tenant, right?