各界 is a compound noun (各 'each' + 界 'boundary/sector') meaning 'all walks of life' or 'all circles' of society. It is used in formal or news-style contexts to refer to people from various professional, social, or political sectors (e.g. 各界人士, 各界代表). Unlike the similar 各行各业 which focuses on occupations/trades, 各界 covers broader social groups including business, education, culture, and government.