Dick i am sorry . its not different set of results , its same result in the different order.
Randomization , I will give you an example.
You own a company(Insurance provider) , many agents are working in your company and you have a online application where in end user or the customer or a common person wants to check the agent detail in there locality using(zip code,first name,last name...etc)
When you execute a query on the table you will get set of agents which are in that particular zip code.If the agent list is big , you can show first 10 - 15 agents details on 1st page and remaining details in next pages. Since there is a high probability that the end user will choose the agents which are in 1st page and they will not browse further. Other agents will loose the oppurtunity to get the customer.
In this case we can go for the randomiztion logic , each time u execute a query u get a same results in different order.
Hope this helps!!!!