newbie's question

hi:) I use fdisk to add a new partion on a image file. I find the start of partion 1 is alwayes set to 63 by default. That means partion 1 start at 63*512=32256 byte. Here is my question: 1. The region from 512th bytes to 32256th bytes will do what ? Why partion 1 don't follow MSR's location ? 2. The image's magic number is at which offset ? Thanks!