Harikrishna 'trades' advantages: he trades his strong bishop, but in return, if we take a look at the remaining pieces on the board, he gets an active rook on the seventh rank and a better knight than the bishop. The e5-square is also now available for the knight!
The central knight joined by the weakness along the seventh rank gives White a clear advantage.
Transformation of advantages. The black c-pawn was a weakness but it could not be attacked conveniently. White trades the pawns in order to activate the king and gives him a penetration route.
A fine and subtle move. Gligoric is not in a hurry. Covering the b5-square, so we stop ...Kb5 after b4+ so Black does not have any counterplay.
4...c5 5.b5 and White is winning. The plan is simple: pushing a5 and a6. Once the pawn arrives at a6, Black is forced to go ...Kc7 to stop b6. Nd5+, followed by Kc4, just kills the game.
Final maneuver: bring the knight to d4, send the black king to f6, and then White is ready to push b5, creating the killer passed pawn on the a-file.