I would like to know what can be figured out from the below Liver function tests.

GGT 16.2 U/L

AST 42 U/L

ALT 36 U/L

Total Bilirubin 0.9 mg/dl

The doctor asked me to do the regular checkups and he said everything is good. But I am curious why those tests are required and what is the current output result meaning from that.

Liver function tests. They could be elevated with liver diseases such as hepatitis, alcoholic liver disease, etc., or with gall bladder disease. Some aspects of the tests are more specific for certain things that others and may just give a clue that further investigation needs to be done. That is the super short version of the answer.

You could do some googling to get more info. Yours are normal, so that's good!

http://en.wikipedia.org/wiki/Liver_function_tests

To start with, the above link; if you have further questions feel free to ask.