Short answers, pulled from the story.
Sherlock Holmes was created by British author Arthur Conan Doyle. The character first appeared in print in 1887 in A Study in Scarlet, published in Beeton's Christmas Annual.
Conan Doyle repeatedly said Holmes was inspired by Joseph Bell, a surgeon at the Royal Infirmary of Edinburgh whom Doyle met in 1877 and worked for as a clerk. Bell was known for drawing broad conclusions from minute observations, just as Holmes does. Sir Henry Littlejohn, Chair of Medical Jurisprudence at the University of Edinburgh Medical School and Police Surgeon in Edinburgh, is also cited as an inspiration.
Conan Doyle killed Holmes in the 1893 story "The Final Problem" because he felt his literary energies should not be directed too much into one channel. The Strand Magazine lost 20,000 subscribers in protest. After eight years of public pressure, Doyle brought Holmes back in 1903's "The Adventure of the Empty House," in which Holmes reveals he faked his death.
Conan Doyle wrote four novels and 56 short stories featuring Sherlock Holmes, with tales appearing from 1887 until 1927. All but one are set in the Victorian or Edwardian eras between 1880 and 1914.
Irene Adler is a retired American opera singer and actress who appears in only one story, "A Scandal in Bohemia." She is notable as one of only a handful of people to best Holmes in a battle of wits and the only woman to do so, which is why Holmes refers to her simply as "the woman."
The exact phrase "Elementary, my dear Watson" never appears in any of the sixty stories by Conan Doyle. The closest the canon comes is in "The Adventure of the Crooked Man" (1893), where Holmes says "Elementary" in response to Watson's exclamation of "Excellent." The full phrase was popularized in part by the Rathbone-Bruce film series from 1939 to 1946.