Information on the Australian Federal police check can be found online through the official AFP website along with a range of other websites that can provide you with detailed information on everything you would like to find out about police checks. Usually, immigration officials would require that you have a police check but it is not restricted to immigration as there is also a number of professions that would make you go for it.
The thing you need to understand is that, it is not an optional thing for you to go for as your profession or your job may entirely depend upon it. So, it may be necessary for you to at least get it provided that you qualify for it. In order to qualify for the AFP police check, you will have to be over the age of 16 along with having been a resident of Australia for at least 12 months cumulatively over the last 10 years.
You may want to refer to the official Australian Federal police website for detailed information on everything you require however in order to apply for an actual police check, you are be able to proceed through a range of websites that are authorised to apply on your behalf and you could sometimes speed up the process by proceeding through experienced individuals and companies.