Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The design featured a boiler pressed to 175 lbf/in (1.21 MPa) delivering saturated steam to two outside 14-inch (356 mm) high-pressure cylinders, which exhausted to one 30-inch (762 mm) low-pressure cylinder inside the frames. All three cylinders had a stroke of 24 inches (610 mm); the high-pressure cylinders drove the rear wheels, while the low-pressure drove the leading driving wheels. As the two pairs of driving wheels were not connected, the locomotives were "duplex drive" or "double-singles".
The locomotive performed poorly for the PRR, being slow and weak compared to the line's other, domestically purchased locomotives, as well as unsuited to the rougher trackage common of U.S. railroads. The unique design of the cylinders made the locomotive difficult to operate and maintain, making it unpopular among the road's engineers and management staff. The locomotive was scrapped in 1897.
Notes
Oswald Nock, et al. Railways at the Turn of the Century, 1895-1905. Blandford P., 1969.
Baxter, Bertram (1979). Baxter, David (ed.). British Locomotive Catalogue 1825–1923, Volume 2B: London and North Western Railway and its constituent companies. Ashbourne, Derbyshire: Moorland Publishing Company. ISBN0-903485-84-2.