Short answers, pulled from the story.
A thrust fault is a type of reverse fault where older rocks are pushed above younger rocks across a break in the Earth's crust. The defining difference is angle: thrust faults dip at 45 degrees or less, whereas steeper reverse faults exceed that threshold. When the dip drops below about 15 degrees from horizontal and displacement reaches the kilometer range, the structure is specifically called an overthrust fault.
The 1994 Northridge, Los Angeles earthquake was caused by a previously undiscovered blind thrust fault. Blind thrust faults are particularly dangerous because their fault plane terminates before reaching the Earth's surface, leaving no visible surface evidence until rupture occurs.
Recognition of thrust faults developed more or less simultaneously among geologists working in several mountain regions during the 1880s. Key figures include Arnold Escher von der Linth, Albert Heim, and Marcel Alexandre Bertrand in the Alps; Charles Lapworth, Ben Peach, and John Horne on the Moine Thrust in the Scottish Highlands; Alfred Elis Tornebohm in the Scandinavian Caledonides; and R.G. McConnell in the Canadian Rockies. Archibald Geikie coined the term "thrust-plane" in 1884.
A blind thrust fault is a thrust fault whose fault plane ends before reaching the Earth's surface, so it produces no visible surface rupture or offset. Because they leave no surface evidence, blind thrust faults are difficult to detect until they rupture. The 1994 Northridge earthquake in Los Angeles was caused by one.
Klippen (singular: klippe) are isolated, island-like remnants of an upper thrust sheet left behind after erosion removes most of the overlying block. A fenster, also called a window, forms when erosion exposes only a small area of the underlying block through the upper thrust sheet. Both features are products of erosion acting on overthrust terrain.
Large overthrust faults occur in orogenic belts produced by continental collisions or subduction zone accretion. The Himalayas, the Alps, and the Appalachians are prominent examples. Thrust faults are also found in foreland basins marginal to these mountain belts, in accretionary wedges at ocean trench margins, and in cratonic settings where deformation has advanced into intracontinental areas.