The passage descends from Cicero's De Finibus Bonorum et Malorum, chopped up and reshuffled until it looks like Latin but says nothing coherent. The 'letter shapes' distribution roughly matches English, so line lengths look realistic.
Use lorem ipsum for wireframes and early mock-ups; switch to real (or realistic) copy as soon as content is available, because word choice heavily changes visual balance.
Alternative placeholder generators exist for anyone who finds fake Latin distracting — bacon ipsum, hipster ipsum, corporate ipsum.