Short answers, pulled from the story.
Opus sectile is a decorative technique in which materials such as marble, mother of pearl, and glass are cut into larger shaped pieces and inlaid into walls or floors to create patterns and images. Unlike tessellated mosaic, which builds up an image from thousands of small, uniform tiles, opus sectile uses larger pieces that each define a distinct section of the design.
Opus sectile first appeared in Rome in the opening decades of the 1st century BC, when builders began laying stone slab floors. Under Augustus, its use expanded into the flooring of public buildings.
The Basilica of Junius Bassus in Rome preserved a large set of fourth-century panels, including one depicting an elaborate chariot. A series of fourth-century glass panels found at Kenchreai, the eastern Corinthian port, is considered particularly remarkable, depicting Homer, Plato, Nilotic landscapes, and harbour cities. The basilica of San Miniato al Monte in Florence features the related Cosmatesque style.
The Kenchreai panels are a series of fourth-century CE panels in glass opus sectile, discovered during excavations at the eastern Corinthian port of Kenchreai in the 1960s. Found at what may have been a sanctuary of Isis, they depict scenes of Homer, Plato, Nilotic landscapes, harbour-front cities, and geometric compositions.
After Rome's decline, opus sectile continued in Byzantine churches, primarily in floor designs. In Persia, the technique was known as Mo'araq and was practiced by the Timurids, the Qara Qoyunlu, and the Aq Qoyunlu dynasties during the 14th and 15th centuries. From Byzantium, the Cosmatesque style carried it back to Sicily and the Italian mainland in the 12th century.
Charles Hardgrave was a noted designer who worked in opus sectile through the Arts and Crafts movement in late 19th-century England. His designs were executed by James Powell and Sons at the Whitefriars Glass Works.