Short answers, pulled from the story.
Roman mosaics are constructed from geometrical blocks called tesserae, cut from natural stone, brick, tile, pottery, marble, or glass, with occasional use of precious metals such as gold. The predominant colors produced were blue, black, red, white, and yellow.
The Bardo National Museum in Tunis holds an especially large collection of Roman mosaics, drawn from large villas in modern Tunisia. Many floor mosaics also survive at sites in Pompeii and Herculaneum in Italy.
The Alexander Mosaic, from the House of the Faun in Pompeii, depicts the Battle of Issus between Alexander the Great and the Persian king Darius III. It is one of the most celebrated examples of Roman figurative mosaic work.
An emblem is a small mosaic featuring a genre scene or still life, made with particularly thin tesserae and set into a central or prominent position within a larger mosaic panel. It served as the visual focal point of the entire composition.
Fifty-seven floor mosaics in the style of labyrinths are known, catalogued by German archaeologist Wiktor Daszewski in 1977. The majority are found in private homes and bathhouses across the Roman Empire.
The floor mosaic from a villa at Hinton St Mary in Dorset, England, dated to the early 4th century AD, is one of the earliest examples of Early Christian art in mosaic. It depicts Christ with a Chi-Rho symbol and is now in the British Museum.