Classical Variation (3...Qa5)

The idea

After 3...Qa5 4.d4 Nf6 5.Nf3 Bf5, Black has the main line's typical setup: the queen on a5 pins the knight on c3 to White's king along the a5-e1 diagonal, and the bishop is outside the pawn chain. ...c6 and ...e6 usually follow.

Plans for White

Develop with Bc4 and Bd2, castle, and look for Ne5 or Bd2 with Nd5 tricks against the queen on a5. Ne5 with g4 is an aggressive try (Lichess's Grünfeld Variation), chasing the bishop on f5 and gaining space on the kingside.

Plans for Black

Play ...c6 to give the queen a retreat on c7 and to cover b5 and d5, then ...e6, ...Bb4 or ...Be7, ...Nbd7 and castle. The structure is like a Caro-Kann, and both sides may castle on either side.

Watch out for

For Black, the queen on a5 being trapped or hit. With Bd2, White can threaten Nd5 or Nb5 discovering an attack on the queen, so ...c6 is useful early.

For White, the pin on c3. Until Bd2 or castling breaks it, the knight on c3 can't move without exposing the king, and ...Ne4 or ...Bb4 can add to the pressure on it.