Rattlesnake Plants (Calathea Lancifolia) are native to the tropical rainforest floors of Brazil. They get their name for the striking spotted pattern on its leaves. Its leaves have deep purple undersides, not uncommon in Calatheas. Itd leaves have ruffled/wavy edges not dissimilar to its cousin, the Furry Feather.
Like most other calatheas, they've evolved to grow under the dappled canopy of taller trees, and as Prayer Plants do, Rattlesnake Plants will fold up their leaves at night and unfurl them the morning to absorb light.
The shaded, moist environment of its native habitat give us a clue as to how to keep this plant most happy: maintain moist soil and a humid environment (something to combat with your AC), and bright indirect light (the more the better, but this plant will not do very well under any direct sunlight at all).