The chuck refers to the metal part located at the end of the drill, holding the drill bit or any other accessory compatible with your machine. It comes in a standard size with the purchase of the device according to its power, but this element can also be replaced if necessary. There are 3 types: the hand-tightening chuck, the key chuck, and the keyless chuck.
With the hand-tightening model, there is a ring on the chuck, you simply turn it to open or close the jaws. For the key model, there is a special key placed between the material in question and a toothed wheel allowing to tighten and loosen each of the tool's jaws around the bit or drill. When it is keyless, the chuck can easily be mounted and dismounted in a single gesture and without a key. This type is becoming more common because of the very practical aspect of its use. On the other hand, when changing this tool, it is recommended to fully open it first, then remove the screw that is usually inside. Then, unscrew the chuck fixed to the motor axis of the drill and install the new one following the factory instructions. Finally, know that for usual tasks, a 10 mm model is largely sufficient. However, it is advisable to also have a 13 mm model, notably offered by the Wolfcraft brand for more powerful drill drivers and for possible more significant work.