Short answers, pulled from the story.
El Greco was a Greek painter, sculptor, and architect of the Spanish Renaissance, born Doménikos Theotokópoulos in 1541 and regarded as one of the greatest artists of all time. He often added the word Krḗs, meaning Cretan in Ancient Greek, to his Greek signature.
El Greco was a nickname meaning "The Greek". The artist himself normally signed his paintings with his full birth name, Doménikos Theotokópoulos, in Greek letters rather than the nickname.
El Greco was born in 1541 on Crete, in either the village of Fodele or Candia, then part of the Republic of Venice. He died in Toledo, Spain, on the 7th of April 1614, aged 72, and was buried in the Church of Santo Domingo el Antiguo.
El Greco's best-known work is The Burial of the Count of Orgaz, for which he received the commission on the 12th of March 1586. Other major works include View of Toledo, Opening of the Fifth Seal, The Trinity, and The Assumption of the Virgin.
Philip II of Spain disliked El Greco's Martyrdom of St. Maurice and placed it in the chapter-house rather than its intended chapel, giving him no further commissions. Some scholars suspect Philip disliked living persons in a religious scene, while others say the work prioritized style over content against Counter-Reformation rules.
El Greco influenced Pablo Picasso, who studied his Opening of the Fifth Seal while working on Les Demoiselles d'Avignon and said El Greco's structure is Cubist. He is regarded as a precursor of both Expressionism and Cubism, and Paul Cézanne was called his spiritual brother across the centuries.
El Greco painted tortuously elongated figures and fantastic pigmentation that puzzled his contemporaries, and later Spanish commentators called his mature work "contemptible" and "ridiculous", a view that hardened into talk of "madness". Ophthalmologists August Goldschmidt and Germán Beritens even attributed the elongation to vision problems such as astigmatism.