Short answers, pulled from the story.
The Czechoslovak Republic emerged on the 14th of November 1918 as the only democracy remaining in Central and Eastern Europe. Tomáš Garrigue Masaryk became the nation's first president and championed a democratic republic uniting Czechs and Slovaks. The state featured a diverse population with Czechs making up 51% and Slovaks 16% of the total.
Britain and France ceded the Sudetenland to Nazi Germany in the Munich Agreement on the 29th of September 1938. This decision crippled Czechoslovakia's defenses and led to the German occupation of the border region in October 1938. By mid-1939, the remainder of the country was dismembered and the Slovak State was proclaimed on the 14th of March 1939.
The Communist Party of Czechoslovakia seized power in a coup in February 1948 and transformed the nation into a Marxist-Leninist state under Soviet domination. Klement Gottwald led the party which maintained the fiction of political pluralism through the National Front. The Beneš decrees subsequently abrogated citizenship for people of German and Hungarian ethnic origin, leading to the expulsion of over 2 million people.
Alexander Dubček initiated the Prague Spring on the 5th of January 1968 to introduce greater political participation and expression. Soviet troops and other Warsaw Pact countries invaded Czechoslovakia on the night of the 21st of August 1968 to end the liberalization. The invasion forced the Communist Party leadership to make concessions to the Soviet Union and gradually put the brakes on their earlier liberal policies.
The Velvet Revolution began on the 17th of November 1989 with student demonstrations that quickly gained momentum. Thousands of citizens took to the streets to demand change and the top Communist leaders resigned on the 28th of November 1989. This event ended 41 years of communist rule in Czechoslovakia.