It's the Cantonese pronounciation of 光復香港，時代革命
Which means Liberate Hong Kong, the revolution of our times.
It all started from the Anti-Extradition protest since June.
People were typing it in Chinese online at the first place, but there were a lot of
mainlanders using VPN to post horrible shits, like supporting
Hong Kong's riot police and threatening protestors on IG and FB, and they even hacked a lot of web pages. (While they don't have any ideas about what people are going through in Hong Kong)
So Hong Kong people started to use Hong Kong language, and because it's different from Chinese Pinyin, so mainlanders can't read.
MOST IMPORTANTLY, we really appreciate everyone abroad for helping us spreading the news and having our back.
*people marching peacefully*
Group A of people: 'Gwong Fuk Heung Gong'
Group B of people: 'Si
Doi Gak Ming'
gwong fuk heung gong, si doi gak ming