aaa authorization config

[ZogoHUN01]

Dear Friends,

Can somebody explain me clearly what will make this config? 

aaa new-model
 aaa authorization command 15 group tacacs+ none
 no aaa authorization config-commands

What will be the result when a user step into this device? 

[balaji.bandi]

here is some example behaviours :

http://www.dslreports.com/faq/9815