Short answers, pulled from the story.
On the Origin of Species was first published on Thursday the 24th of November 1859. It was priced at fifteen shillings, with a first printing of 1,250 copies, all of which were taken up by booksellers at Murray's autumn sale before the official publication date.
On the Origin of Species argues that species are not fixed but evolve over generations through natural selection. Darwin showed that heritable variation exists within populations, that more individuals are born than can survive, and that those better suited to their environment are more likely to reproduce and pass on their traits, gradually producing new species over time.
Darwin conceived the core of his theory by late 1838 but did not publish until 1859. Science historian John van Wyhe found that the idea of a deliberate delay only dates back to the 1940s; Darwin's contemporaries considered the time he took reasonable. Darwin always finished one book before starting another, spent eight years studying barnacles, and only had time to work on evolution full-time from September 1854.
On the 18th of June 1858, Darwin received twenty pages from Wallace describing an evolutionary mechanism similar to his own theory of natural selection. Lyell and Hooker arranged for a joint publication at the Linnean Society on the 1st of July 1858, combining Wallace's pages with extracts from Darwin's 1844 Essay and his 1857 letter to Asa Gray. This prompted Darwin to write an abstract of his full work, which became On the Origin of Species.
Six editions were published during Darwin's lifetime. The second edition appeared on the 7th of January 1860, and the sixth and final edition was published on the 19th of February 1872. By Darwin's death in 1882, the book had earned him nearly £3,000.
The phrase "survival of the fittest" first appeared in the fifth edition of On the Origin of Species, published on the 10th of February 1869. Darwin credited the phrase to philosopher Herbert Spencer, who had coined it in his Principles of Biology published in 1864.