Short answers, pulled from the story.
Gary Gygax and Dave Arneson created Dungeons & Dragons which was first published in 1974 by Tactical Studies Rules. The game emerged from miniature wargaming with a limited production budget of only $2000.
Dungeons & Dragons has released multiple editions including Advanced Dungeons & Dragons in 1989, D&D 3rd edition in 2000, and D&D 4th Edition on the 6th of June 2008. The most recent edition launched during the second half of 2014 coinciding with D&Ds 40th anniversary while a backwards-compatible evolution of 5th edition will arrive in 2024 to mark the 50th anniversary.
Christian groups accused Dungeons & Dragons of promoting devil worship witchcraft suicide and murder throughout various periods in its history leading to social ostracism for fans. Research by psychologists starting with Armando Simon concluded that no harmful effects are related to playing D&D despite these rumors regarding players having difficulty separating fantasy from reality.
As many as six million people played the game in 2007 according to available records while the year 2017 marked the most number of players in its history with 12 million to 15 million in North America alone. Consumers spent more than $1 billion on D&D products by 2004 with the game played by more than 20 million people.
TSR began legal action in the mid-1980s to prevent others from publishing compatible material though it never brought any court cases to completion instead settling out of court every time. Wizards of the Coast made the d20 System available under the Open Game License in 2000 allowing authors free use of mechanics when writing games and supplements.