Why is the queen considered lost? In this game, white just moved the queen from b7 to c6, and the computer marks this as a &quot;critical blunder&quot; (and suggests that the bishop should take the knight). In this position it considers the queen lost, but it doesn't say much how. It says black should move their rook to c8, but then it seems to me the queen can go to b5, and from there on it's hard to take it.
The black rook can then move to b8 and the queen can go back to c6. If the rook doesn't move, it seems to me the queen can escape: if the white queen moves then it becomes a queen trade, and if the black knight moves then the queen can play a4 and then escape to c2 (for instance).
How can the black take the white queen in this configuration? (black to move)
r2q1rk1/p3b1p1/2Q1p2p/2npp3/4P3/2PPBN1P/PP3PP1/R3R1K1 b - - 0 1

1... Rc8 2. Qb5 Rb8 3. Qc6 Rb6!

Now white's queen is trapped.
As @Joffan has pointed out in the comments and as many have probably seen, immediately trapping the queen is not the end to this game:
r2q1rk1/p3b1p1/2Q1p2p/2npp3/4P3/2PPBN1P/PP3PP1/R3R1K1 b - - 0 1

1... Rc8 2. Qb5 Rb8 3. Qc6 Rb6 4. Qxc5 Bxc5 5. Bxc5 Rxb2 6. Bxf8 Qxf8

A more convincing alternative seems to be sacrificing the rook for the knight.
 r2q1rk1/p3b1p1/2Q1p2p/2npp3/4P3/2PPBN1P/PP3PP1/R3R1K1 b - - 0 1

1... Rc8 2. Qb5 Rxf3 3. gxf3 Rb8 4. Qc6 Rb6 5. Qxc5 Bxc5 6. Bxc5 Rxb2