A conditional move is a move that you plan as a reply to a certain move of your opponent. For example, if you have Black in a freshly started game, you plan to answer c5 if he plays e4. And if he continues with Nf3 you would answer that move with d6.
You can advice the PlayChess server to make these conditional moves (c5 and d6) for you. But if your opponent deviates from your conditional move sequence (by not playing 1.e4 or not playing 2.Nf3), the PlayChess server will not do anything. Instead, you will have to enter your move yourself, just as you normally would do.
Hint. Conditional moves are a members only feature.
If the PlayChess server finds your conditional moves, it automatically makes them for you, as long as the game follows your expectations. The server just makes your planned moves, nothing else; it does not "invent" its own moves. However, it makes your moves immediately, since it is always "on line". Everything else is just as usual:
The move sequence page
You enter conditional moves on the move sequence page. The easiest way to get there is checking the Conditionals checkbox on the move dialog at the right of the game page. When you click the Move button, your move is stored and you see the page for entering a conditional move sequence.
But if you forgot to click the Conditionals checkbox, simply go back to that game. While your opponent is to move, you see a link Conditional moves beneath the chess board, leading you to the same page as above.
Entering conditional moves
On the move sequence page the chess board is on the left and the (empty) list of moves on the right. You see the position after your last move (or the start position). Your opponent is to move.
Now click in the (most probable) move of your opponent by clicking on the start and end field of the moving piece. This move appears in long algebraic notation on the right side. Then do the same for your planned reply. Then again for your opponents move, and again for your reply, and so on until you think it's enough (up to 10 moves are possible).
Click on the Store button to save your move sequence to the database.
List of conditional moves
The following page displays all your conditional moves sequences (currently: one). From here you can enter new sequences, delete all move sequences, or return to the game.
Random move selection
If you enter more than one move sequence with different replies to the same move of your opponent, the PlayChess server will select one of these replies at random.
For our example you are a Sicilian specialist that equally likes the Najdorf and the Dragon defense. The Moves 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 have already been made. On the game page you make your move 4...Nf6 and check the Conditionals checkbox. On the move sequence page you enter the following move sequences:
So you entered two different replies (a6 and g6) to the same move Nc3. If your opponent plays Nc3, the PlayChess server fetches the two matching move sequences and randomly selects one of these. The move sequence starting with 5.f3 does not match and is discarded, anyway.
Random move selection is just a "gimmick" in game-specific conditional moves. It will be much more important in the upcoming Opening repertory. There, you will be able to store your opening repertory on the PlayChess server, which will be used to generate conditional moves. In this situation, "random move selection" will often be used to decide which of your prefered openings is used for a specific game.