What is difference b/w initial & signature?--where to apply both of these?

I am a government employee and joined new job today. I was asked to initial on "must roll". I asked the gentleman that should I do my signature what is done on my CNIC and bank accounts. He told me you can initial/sign it whatever you want! It is an initial and you will have to sign it since today onwards daily and you will have to report on early morning. I just initialed my name's first letter with lining. So, I want to ask you, what is the difference between initial and signature? Can we use two signature on the same job. One is for must roll and the second one is for bank accounts, legal proceedinngs etc.?

Detailed and to the point answer would be obliged.