Short answers, pulled from the story.
Estonia declared independence in February 1918, followed by Latvia and Lithuania in 1918 as well. Their independence was consolidated after wars that concluded in 1920. Soviet occupation ended that independence in June 1940.
The Baltic Way was a human chain formed on the 23rd of August 1989, in which two million people linked hands across 600 kilometers from Tallinn in Estonia to Vilnius in Lithuania. It was part of the Singing Revolution, a campaign of civil resistance against Soviet rule, and fell on the 50th anniversary of the Molotov-Ribbentrop Pact.
Between 1940 and 1953, the Soviet central government deported more than 200,000 people from the Baltic states to remote locations across the Soviet Union. At least 75,000 more were sent to Gulags, accounting for roughly 10% of the adult Baltic population.
The Nazi German occupation resulted in the murder of over 190,000 Lithuanian Jews, nearly 95% of Lithuania's pre-war Jewish community, and 66,000 Latvian Jews. These killings took place through ghettoisation and mass shootings carried out during the German occupation from 1941 to 1944.
All three Baltic states became NATO members on the 29th of March 2004 and joined the European Union on the 1st of May 2004. They are the only post-Soviet states to be members of both organizations.
Latvian and Lithuanian are the only living members of the Baltic branch of the Indo-European language family. Estonian belongs to a separate Finnic language family, closely related to Finnish. The three languages are not mutually intelligible, and their divergent origins reflect centuries of distinct ethnic and political histories.