Short answers, pulled from the story.
Tea first arrived in Russia as a documented diplomatic gift around 1636-1638, when a Mongolian ruler donated four poods (65-70 kg) of tea to Tsar Michael. The envoy Vassili Starkov carried the gift after the Mongolian Khan insisted he accept it despite his initial refusal.
Zavarka is a strong tea concentrate brewed in a small teapot during the first step of Russia's traditional two-stage brewing process. Each person then pours some zavarka into their cup and dilutes it with hot or cold water to their preferred strength. The same leaves can be brewed up to three times, though most drinkers consider repeat brews inferior in quality.
A samovar is a large heated vessel used to boil and keep water hot for brewing tea. It was the standard tool for Russian tea preparation until the middle of the 20th century, when gas stoves and kettles displaced it in most homes. On Russian trains, conductors still serve tea using hot water from a samovar at the end of the carriage.
Russian Caravan is a tea originally imported from China via camel caravan, a journey that took sixteen to eighteen months. During transit, the tea absorbed smoke from the caravan's campfires, creating its distinctive smoky flavor. Today that flavor is reproduced through oxidation or by blending keemun or an oolong with Lapsang Souchong or Tarry Souchong.
Russian Tea in the United States is a hot beverage made from black tea, orange juice or orange peel, cinnamon, and cloves, with no documented connection to Russia itself. References to it appear in American newspapers and cookbooks dating to the 1880s. It is especially popular in the Southeastern United States, where it is traditionally served during Advent and Christmastide.
Chifir is an extremely high-concentration brew of tea consumed in Russian prisons as a substitute for alcohol, which is typically prohibited. It functions as a traditional mind-altering substance within that environment.