Occupy Central: An abbreviation of “Occupy Central with Love and Peace” it is an organisation started by Benny Tai in 2013 in anticipation of the elections not being carried out to international standards. It is one of the two main groups protesting. (wikipediaofficial siteofficial twitter)
Scholarism: A student activist group formed in 2011 by secondary school students. The other main group protesting. (wikipediaofficial twitter)
Central / Admiralty / Causeway Bay / Mong Kok / Wan Chai: Main business and shopping areas in Hong Kong, known for being incredibly busy. Together they make up the central hub of movement in HK. (MTR map)
MTR: Hong Kong’s underground train transport system, similar to New York’s Subway or London’s Underground.
Chief Executive: The position Hong Kong is fighting to elect fairly, it is the top political position in Hong Kong. (wikipedia)
Leung Chun-ying / CY Leung: The current Chief Executive of Hong Kong. Viewed by the majority of HK as a “communist puppet” or as someone being controlled by the CCP. (wikipedia)
689: The number of electoral votes CY Leung won by, a very auspicious number which translates roughly to something like “the long road of prosperity”. Many HKers believe it to be suspiciously auspicious, and use it as a pejorative against CY Leung.
One Country, Two Systems: Is the system Hong Kong is governed under now. It is essentially where Hong Kong is officially part of China, however it is governed by a democratic government. (A more detailed explanation here)