Adjustable Wrench is a spanner with a jaw of adjustable width, allowing it to be used with different sizes of nuts & bolts, rather than a single size as with a conventional fixed spanner. The same wrench can be used with both metric & imperial fasteners.
Ensure that fixed jaw leads the rotation & movable jaws follows the fixed jaw. This way , there will be less stress on the movable jaw which is not supported as ruggedly as the fixed jaw.