The Truth – Extinction Rebellion has a great introductory video on ER and what and why.
Wikipedia’s definition: https://en.wikipedia.org/wiki/Extinction_Rebellion:
“Extinction Rebellion (abbreviated as XR) is a socio-political movement with the stated aim of using civil disobedience and nonviolent resistance to protest against climate breakdown, biodiversity loss, and the risk of social and ecological collapse.
Extinction Rebellion was established in the United Kingdom in May 2018 with about one hundred academics signing a call to action in support in October 2018, and launched at the end of October by Roger Hallam, Gail Bradbrook, Simon Bramwell, and other activists from the campaign group Rising Up!. In November 2018, 5 bridges across the Thames River in London were blockaded. In April 2019 Extinction Rebellion occupied 5 prominent sites in central London: Piccadilly Circus, Oxford Circus, Marble Arch, Waterloo Bridge and the area around Parliament Square.
Citing inspiration from grassroots movements such as Occupy, Gandhi’s Satyagraha, the suffragettes, Gene Sharp, Martin Luther King and others in the civil rights movement, Extinction Rebellion wants to rally support worldwide around a common sense of urgency to tackle climate breakdown. A number of activists in the movement accept arrest and imprisonment, similar to the mass arrest tactics of the Committee of 100 in 1961.”
The movement uses a circled hourglass, known as the Extinction Symbol, to serve as a warning that time is rapidly running out for many species.