Short answers, pulled from the story.
Robert Armin (c. 1568-1615) was an English actor who replaced Will Kempe in the Lord Chamberlain's Men around 1600. He is credited with originating Shakespeare's major fool roles after that date, including Touchstone, Feste, and Lear's Fool, and his distinct style of philosophical, witty comedy is believed to have shaped how Shakespeare wrote those characters.
Armin is credited with Touchstone in As You Like It, Feste in Twelfth Night, the Fool in King Lear, Lavatch in All's Well That Ends Well, and possibly Autolycus in The Winter's Tale, Thersites in Troilus and Cressida, the Porter in Macbeth, and the Fool in Timon of Athens. Some scholars also argue he created the role of Iago in Othello.
Armin published Fool Upon Fool in 1600, reissued in 1608 as A Nest of Ninnies, which documented natural fools he had personally encountered. He also published Quips upon Questions in 1600, demonstrating his comedy style, and wrote the play The History of the Two Maids of More-clacke around 1597. In A Nest of Ninnies he drew a key distinction between the fool natural and the fool artificial.
Kempe represented the older tradition of the rustic, physical clown. Armin shifted the role toward a domestic wit whose comedy came from wordplay, multiple personas, and philosophical observation rather than direct audience combat or physical buffoonery. This change is sometimes described as the "taming of the clown."
Armin was born around 1568 in King's Lynn to a tailor father and was apprenticed in 1581 to John Lonyson, a goldsmith who served as Master of Works at the Royal Mint in the Tower of London. He finished that apprenticeship in 1592 and had already gained a literary reputation by then, with his name attached to a religious tract in 1590 and mentions as a ballad writer in 1592.
Robert Armin was buried on the 30th of November 1615. His burial is recorded in the registers of St Botolph's Aldgate in London, the parish where he had lived. Three of his children named in that same parish register appear to have died before adulthood.