Electric wrench, sometimes also referred to as an "impact wrench", is an electrical tool designed for tightening and loosening nuts and bolts. Wrenches differ from regular drills and screwdrivers in their ability to generate a high level of torque, making them ideal for working with fasteners. Here are the key characteristics and functions of wrenches:

1. Motor and Power Source: Electric wrenches can be corded, operating from an electrical outlet, or cordless, with a built-in battery. Their powerful electric motors create a high level of torque, allowing for easy tightening and loosening of nuts and bolts.

2. Adjustable Torque: Most wrenches are equipped with a torque adjustment feature, enabling the user to set the tool to a specific torque level based on the task and material.

3. Impact Mode: Many wrenches also have an impact mode that provides additional rotational force when fastening and unfastening bolts, which is particularly useful for dealing with stuck or stubborn fasteners.

4. Various Sizes and Types of Nuts and Bolts: Wrenches are suitable for working with a variety of nut and bolt sizes and types. They are used in mechanics, construction, automotive repair, and other fields.

5. Accessories: Wrenches may come with various sockets and accessories for handling different types of fasteners.

6. Mobility and Efficiency: Wrenches significantly increase work efficiency when dealing with a large number of bolts, which is particularly beneficial in industrial and automotive applications.

Wrenches are an indispensable tool in mechanics, construction, and other industries where tightening and loosening fasteners with high torque is required.