On November 7th the Bolshevik Revolution started in Petrograd in Russia.
The revolution is also known as the October Revolution. This is because, at that time, Russia was using the Julian Calendar, and 25th October on that calendar is November 7th on the Gregorian Calendar.
The revolution was the second revolution to happen in Russia that year. This one did not overthrow the Tsar, Alexander II. He had been overthrown in the February Revolution earlier in the year and had been replaced by a new government, primarily of nobles and aristocrats. Petrograd was the current capital of the provisional government which replaced the Tsar.
The Bolshevik Revolution was that of the workers and led to the creation of the Union of Soviet Socialist Republics - eventually. It also started the Russian Civil War.
Image: Viktor Bulla [Public domain], via Wikimedia Commons (commons.wikimedia.org/wiki/File:Red_Guard_Vulkan_factory.jpg)