Hololive isn't the first Vtuber company (Kizunai's group predated it) and they weren't the first to do Live 2D vtubers (Nijisanji did that) but they effectively merged idol culture into vtubers. The terms graduation, oshi, etc are all sourced from idol culture and Hololive brought it in. They have 2 sections (Hololive and Holostars), 3 branches (Japan, Indonesia, and English), and a total of 19 generations in total (Including the Holostars).
Some standout comedic moments include: