解放 is deeply tied to Chinese modern history. '解放前' (before liberation) and '解放后' (after liberation) refer to before and after the founding of the PRC in 1949. 中国人民解放军 (PLA) is the country's military.
usage
解放 can be used figuratively: 解放思想 (liberate thinking), 解放双手 (free one's hands). In modern Chinese, it often means 'to free up' in casual contexts.