PGN is the universal text format for chess games, every chess engine, every chess server (chess.com, lichess), every analysis tool reads it. A PGN file is a sequence of game blocks; each block has 7-tag headers (Event, Site, Date, Round, White, Black, Result) followed by the moves in algebraic notation. A single PGN file can contain thousands of games.
How to open
chess.com, lichess.org (paste it into the analysis board), ChessBase, Scid, every chess engine. Plain text in any editor.