An outpost gains its value from permanence. Because no enemy pawn can challenge the piece occupying it, a well-placed knight on an outpost can dominate the position for many moves. The d5 and e5 squares (d4 and e4 for Black) are classical outpost targets, but any secure advanced square can serve as an effective outpost.
Knights benefit most from outposts because they cannot be driven away by enemy bishops or rooks the way a bishop on an outpost might be challenged. A knight on d5 or e5, supported by a pawn on c4 or f4, can control up to eight squares deep in the opponent's territory, restricting piece mobility and supporting tactical operations.
Creating outposts requires careful pawn play. You must induce the opponent to advance or exchange the pawns that could contest the outpost square. Once established, an outpost knight often becomes a strategic anchor around which the rest of your position revolves.