Short answers, pulled from the story.
The territory of modern Abkhazia formed part of the ancient Kingdom of Colchis between the 9th and 6th centuries BC. Greek traders established colonies along the Black Sea coast at Pitiunt and Dioscurias around the 6th century BC.
Large numbers of Muslim Abkhazians emigrated to the Ottoman Empire between 1864 and 1878 following the Russian annexation. This process known as Muhajirism left large areas of the region uninhabited before other groups migrated to resettle the vacated territory.
Between 1922 and 1926, the share of Abkhaz increased from 19.8% to 27.8% of the population while ethnic Georgians decreased from 42% to 36%. By 1952 over 80% of top officials were ethnic Georgians despite Abkhazians dominating governance with only 17.8% of the region's population.
War broke out in August 1992 when the National Guard of Georgia entered Abkhazia with the goal of freeing captive Georgian officials. The Abkhaz separatist government retreated to Gudauta where a Russian military base was located after Abkhaz troops opened fire first according to Darrell Slider.
The population of Abkhazia reduced from 525,000 in 1989 to 216,000 in 2012 due to mass expulsion and violence against Georgians. About 5,000 people were killed, 400 went missing, and up to 250,000 ethnic Georgians were expelled from their homes during the conflict.
Russia recognized independence of Abkhazia on the 26th of August 2008 following the Russo-Georgian War. This recognition led to the annulment of the 1994 ceasefire agreement and termination of UN and OSCE monitoring missions.