Short answers, pulled from the story.
Egyptian hieroglyphs were the formal writing system of ancient Egypt, combining ideographic, logographic, syllabic, and alphabetic elements. The system used more than 1,000 distinct characters during much of its history, though by the Greco-Roman period the number had expanded to more than 5,000 signs.
Proto-literate hieroglyphic symbol systems appeared around the 33rd century BC, with the first decipherable sentence dating to the 28th century BC. The last known hieroglyphic inscription, the Graffito of Esmet-Akhom at Philae, dates to 394 AD. Monumental use ceased after the Roman Emperor Theodosius I ordered the closing of all non-Christian temples in 391.
Jean-Francois Champollion completed the decipherment of Egyptian hieroglyphs by the 1820s, using the Rosetta Stone as his key source. The Rosetta Stone, discovered by Napoleon's troops in 1799, presented the same text in hieroglyphs, demotic, and Greek, allowing Champollion to compare scripts and recognize that the system was simultaneously figurative, symbolic, and phonetic.
Egyptian hieroglyphs are the ultimate ancestor of the Phoenician alphabet, from which the Greek and Aramaic scripts descended. Through Greek came the Latin and Cyrillic alphabets; through Aramaic came the Arabic and Brahmic scripts. The majority of the world's living writing systems are therefore descendants of Egyptian hieroglyphs.
The Rosetta Stone is an ancient decree inscribed in three parallel scripts: hieroglyphs, demotic, and the Greek alphabet. Napoleon's troops discovered it in 1799 during the Egyptian invasion. Its parallel texts provided the first falsifiable material for deciphering hieroglyphs, enabling scholars including Champollion to identify the phonetic values of individual signs.
Hieroglyphs are thought to be one of only four writing systems developed without outside influence, alongside cuneiform, Chinese characters, and the Mayan script. While some scholars argued that Egypt borrowed the concept of writing from Mesopotamia, glyphs found at Abydos dated between 3400 and 3200 BC challenge the assumption that Mesopotamian writing predates the Egyptian system. The forms of the hieroglyphs are entirely Egyptian in origin, reflecting Egypt's own landscape, flora, and fauna.