Differences in the queries

How do i explain the following different queries like i am teaching a 5 year old kid?

 i) SELECT suser_sname(owner_sid) as 'Owner', state_desc,name as DatabaseName, database_id FROM sys.databases
 ii) SELECT * FROM sys.server_principals
 iii) SELECT * FROM sys.sysusers
 iv) SELECT * FROM sys.sysmembers
 v) SELECT * FROM sys.databases
 vi) SELECT * FROM SYS.SYSLOGINS

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Author: teo93