SQL Server 2008

Because the owner is the root of trust. It is the owner that grants, denies and revokes permission on the object
Links
logins and users

Logins and Users in SQL Server
http://www.sqlservercentral.com/blogs/brian_kelley/2009/04/21/sql-server-security-basics-logins-vs-users/
https://www.youtube.com/watch?v=c3gPdKaLlkg This is quite good
https://www.youtube.com/watch?v=9Zj5ODhv0b0&list=PL08903FB7ACA1C2FB&index=6 good series of tutorials
Beginners SQL Server tutorial
How to locate a table by table name