Making sense of a century and more of census data

As usual, my mum had beaten me to it. I’d been asked to have a root around the online censuses of 1901 and 1911 to see what elements of family history I could find. Instead, my mother had it already done.
Out came the box of documents and here it was, history at my fingertips. I had already looked into the census data for my father’s side of the family and now here, alongside that, were copies of the actual census forms on my mother’s side, as filled out more than a century ago.