You might be surprised to learn that solid wood rarely forms the cabinet box. It's more often used in face frames and doors than in the larger side panel parts. That's because it tends to warp-a special concern in the kitchen where the moisture level changes frequently. But in the doors, using multiple strips of lumber in a variety of sizes can reduce the warp factor. A "floating" panel might also be used. The panel floats because instead of being glued to the doorframe, its edges sit between wooden grooves, allowing the wood to move more freely with changes in the kitchen's humidity.
Box materials typically contain wood chips, other wood by-products, and synthetic additives to make them especially strong and warp resistant. Your options include:
All have solid reputations for durability and screw-holding power, particularly plywood. Medium-density fiberboard has gained a following for its ability to be formed into door and drawer heads and other decorative features. Furniture-grade flakeboard offers a stronger alternative than particleboard, which you'll pay the least for.
Often the door and box will be constructed of different materials. A cabinet door might be solid maple and the cabinet box plywood covered with a maple veneer. The same finish would be applied to both, unifying the look. Or you may decide you want different tones on the door and the sides to add contrast.
You'll want to make sure you know if the finish you like requires a certain base material, and you'll want to check out examples of your manufacturer's work. Beware of staples! Staples will pull apart. You want cabinets with thick panels that have been corner blocked and glued or fastened with screws.