A wrench or spanner is a tool used to provide a mechanical advantage in applying torque to turn bolts, nuts or other hard-to-turn items.
In American English, wrench is the standard term, while spanner refers to a specialized wrench with a series of pins or tabs around the circumference. (These pins or tabs fit into the holes or notches cut into the object to be turned.)
In British English, spanner is the standard term. Hinged tools, such as pliers or tongs, are not generally considered wrenches.
From Pocket Wikipedia, http://www.free-soft.ro/pocket-wikipedia/