Short answers, pulled from the story.
James II became king in February 1685 with widespread backing from Protestant majorities across England and Scotland. His conversion to Roman Catholicism while in exile during the English Civil War did not initially deter his supporters.
The revolution occurred because James II failed to appreciate how much his power relied on support from the landed gentry who were mostly Protestant. His policies appeared to undermine the primacy of the Church of England and Church of Scotland which destabilised all three kingdoms.
William III of Orange was the stadtholder of the main provinces of the Dutch Republic who married James's elder daughter Mary in 1677. He led an expedition that began embarking on the 22nd of September and completed by the 8th of October to take control of the provisional government on the 28th of December.
Parliament declared that in choosing exile James had abdicated and thus vacated the Crown which was therefore offered jointly to William and Mary on the 6th of February. The Convention Parliament assembled on the 22nd of January to debate the issue before reaching this resolution.
James II landed in Ireland accompanied by 6,000 French troops on the 12th of March 1689 where he was backed by the majority Catholic population. His supporters were known as Jacobites and the war in Ireland was accompanied by a rising in Scotland until early 1692.