g. Ngf3 implies "knight in the g-file moves on the square f3"; R1e2 implies "rook on the main rank moves to e2"). For pawns, no letter First is applied; so e4 suggests "pawn moves to the square e4". Prophylactic chess https://mariahxjis937894.wikipublicity.com/5638942/5_simple_statements_about_chess_explained