What is the difference between IELTS 8, IELTS 9, IELTS 10 and IELTS 11 exams?

I am wondering whether this is a serious question or has it been posted in jest ! 

Dileep, there is no such concept or actuality as IELTS 10 and IELTS 11.

The IELTS test is scores are given ranging from 0-9.

0 refers to someone who did not attempt the test. To me, it means the candidate registered but did not appear. 

1 means a NON USER. In my career spanning 20 odd years i have never heard or met anyone who got 1. So, you can get your own conclusion from whta i have just said.

2 is an INTERMITTENT USER. As in band 1, referred earlier, the same applies here, as far as I am concerned.

3 referes to an EXTEREMELY LIMITED user. The same applies here as in above.

4 is a LIMITED USER. Here, reality comes into play. Upto Bnad 3, it is useless. But, for Band 4 , many visa requirement is fulfilled, for example- UKVI spouse visa.

5 means the candidate isa MODEST USER. Many students do get this kind of score but, not in all the modules. 

6 is a person who has generally effective command of the language. Its called COMPETENT USER.

7 is where the fun begins. For PR, this is a prickly thorn for many. It means that if you get Band 7, YOU ARE GOOD.

8 is an enhancement of Band 7. Here you are VERY GOOD.

9 is the Everest. you cannot climb higher. With Band 9, you can proudly say I am an EXPERT.

Dileep, It appears that you heve no idea about IELTS at all. Its called International English Language Testing system and it is an assessmenttest used , mainly, by U.S.A./U.K./Canada/Australia and New Zealand. 

Primarily, these countries tried to shield or filter people coming to their country either for studies, jobs or permanent residency. 

The IELTS test is scored on a scale of 0-9, with 0 being a non-performer and 9 being an expert,as far as usage of the languageis concerned. Important mark-ups are 4/5 for jobs/spouse visa, 6.5 for a student visa and 7/8 for a permanent visa.

There is no such category as IELTS 10 or 11.