Page and sector offsets

I am new to forensics and I can't find any information on what is a sector and page offset. I am using WinHex to investigate a simple disk image and one of the questions I am faced with is "Is the offset 0A1A1E00 a page or sector offset? Why was that type of offset used?" I'm not looking to just be told the answer but was hoping to learn about what this offset is and possible how to tell the difference.