Note: buttons have gone away beginning with Crosswords 4.2 for Windows Mobile in keeping with current Microsoft UI guidelines. All features remain, accessible via the menu.

The flip button (PalmOS only): The flip button flips the board along a line running from the top-left corner to the bottom-right corner, making vertical words horizontal and vice-versa. Some folks find that this helps make moves more quickly.
The values button (PalmOS only): The values button replaces letters on the board with their values. It's required because the squares are too small to display both at the same time. Tap it a second time, or choose the menuitem again, to reverse the effect.
The hint button (PalmOS only): The hint button searches the dictionary using the tiles in your tray and places the highest-scoring move on the board. Click it again to get the next-highest-scoring move, and so on through every move that's possible with your current tiles.
The juggle button (PalmOS only): This button randomly scrambles the tiles in your tray. Try it a few times if you're having trouble spotting any words there.
The board
Bonus squares: Bonus squares improve the score of the move that first places a tile on them. Hold the pen on a bonus square for a half second to see a small window reminding you of the value: double word, triple word, double letter or triple letter. (You can change the colors of bonus squares with the Color preferences dialog.)
Arrow cursor: The black arrow cursor (facing right in the picture on this page) indicates where the next tile tapped in the tray will be placed. Tap an empty square to place the arrow. Tap the arrow to change its direction or to deactivate (hide) it. When you tap a tile in the tray, it replaces the arrow cursor which then moves to the next empty square in the direction it points. If you don't like the arrow cursor, you can disable it by turning off the Enable cursor option in the preferences dialog.
Recent move: The most recent move is indicated by white letters on a black background. In this picture it's the word VILOST.

Blank tiles: On PocketPC, blank tiles show up on the board with tiny black or white vertical lines in their corners. On Palm, they are marked by gaps in the frame around the tile. This is to help you distinguish them from tiles that will have their expected value when incorporated in new words. On the PocketPC board above, the V in YESHIVAS (played vertically down the middle of the board) is a blank. On the Palm board look at the T near the lower left.

Hint region: To limit the region of the board searched by the hint feature, first turn on the feature by checking the Local hints or Hint limits option in the Game preferences dialog. Then use the pen to drag the rectangle on the board, and choose Hint from the Move menu. To remove the rectangle, draw in an upward direction.; The hint region does not effect robot players.; The hint region is currently not available on devices without touchscreens, e.g. Smartphone.
The tray: The tray, below the board, holds each player's current set of tiles. You can drag the tiles to reposition them as you look for words, and can tap one to select it and then tap a square on the the board to place it there. When the first tile is moved from the tray, the points counter appears at the right end. When additional tiles are gone empty space opens up that you can tap to move all tiles back to the tray.
Tile separator: The tile separator (the tall thin line shown at the left edge of the tray, black on PPC and red on Palm in the images above) can be dragged between any tiles. You can do this to help you organize your tiles as you think about your move. But it has a more important role if you're using the hint feature: when searching the dictionary for a move, the hint robot ignores any tiles to the left of the separator. So if, for example, you have a blank and don't want it used in your next move, move it to the left of the separator and you'll only generate hints that don't use the blank.
Points counter: This counter, which is not visible unless at least one tile has been moved from the tray to the board, gives the points that the currently pending move will earn. If the move is illegal (e.g. includes tiles that aren't in a straight line) the counter will show question marks.
The scoreboard: The scoreboard has one entry for each player in the game. While there are still tiles in the pool, and each player is certain to have seven tiles, each player's current score is shown. Once the last tile has been drawn from the pool the scores change to also show the number of tiles the player has left. Hold the pen on a score for a half second to see the player's name and a summary of his/her most recent move.; Beginning with version 4.4, the name of the player whose turn it is is also shown in the scoreboard.
Remaining tiles counter: This counter shows the number of tiles left in the pool. Once that number drops to zero the counter disappears. (At the same time the display of players' scores changes to show the number of tiles each has left.) Tap on the counter to see the same Remaining tiles dialog as produced by the Tiles left menuitem .
Timer: Enabled by the Game preferences dialog, the timer shows how much time is left for the currently selected player (not necessarily the player whose turn it is.)