Margins refer to the outer section of the card i.e the space by the edges
The majority of cards for Inkpact will be cards that contain a logo and/or footer and the area around and just above and below these should be avoided.
When setting up your card on the lightpad/line guide to write, you should align the left edge of the guide paper lines in such a way that it allows you to have a neat left aligned margin so your writing does not come too close to the edge of the card.