The Pilcrow is a typographical character denoting individual paragraphs. The first way of dividing sentences into groups was the ancient Greek paragraphos, a horizontal line in the left margin, which then evolved to the Pilcrow (¶).
In medieval writing, the Pilcrow became an ornamental symbol, elaborately drawn by rubricators after a manuscript had been copied by scribes, who left spaces for the rubricators to fill with embellishments.
As demand and production of books increased, rubricators often ran out of time before they finished all illustrations and places reserved for the Pilcrow were left blank. This meant the Pilcrow became a ghost and the indented paragraph was born instead.
The Pilcrow still crops up in modern text editing. In proofreading it indicates that one paragraph should be split into two or more separate paragraphs. Hidden characters in word processors still use the Pilcrow to represent a new paragraph, lending computerised documents a dignified medieval look.