If you want to see a list of all login names defined on the server, you can use the system view, sys.server_principals as shown in this tutorial exercise:

-- Login with sa

SELECT name, sid, type, type_desc FROM sys.server_principals

WHERE type = 'S';

GO

name sid      type type_desc

-------- ----------------------------------- ---- ---------

sa  0x01      S SQL_LOGIN

ggl_DBA 0x348AF32B3B58CB40B67A5F5B7086B96E S SQL_LOGIN

ggl_Login 0x5EB8701EAEBAA74F86FCF5BD8E37B8C5 S SQL_LOGIN

So you have two login names on the server at this moment.