The pilcrow, ¶, is a handwritten or typographical character used to identify a paragraph. It is also called the paragraph mark, paraph, or blind P.
Three short paragraphs on making gunpowder in the manuscript GNM 3227a (Germany, c. 1400); the first paragraph is marked with an early form of the pilcrow sign, the two following paragraphs are introduced with litterae notabiliores (literally: enlarged letters).
Pilcrow signs in an excerpt from a page of Villanova, Rudimenta Grammaticæ, printed by Spindeler in 1500 in Valencia.
Opening page of Genesis from the Doves Bible (Doves Press, 1902): pilcrow used as a verse marker
A paragraph is a self-contained unit of discourse in writing dealing with a particular point or idea. Though not required by the orthographic conventions of any language with a writing system, paragraphs are a conventional means of organizing extended segments of prose.
Indented paragraphs demonstrated in the US Constitution