Socket wrenches - whether sold individually, as socket sets and wrench sets, or all bundled together in a combined kit - are used for the same jobs as any regular spanner set. In other words, they are designed to make fastening and unfastening various sizes of nuts and bolts easier.
Where socket wrenches differ from standard spanners is that they have an inbuilt ratcheting mechanism. A ratcheting design means that the wrench head locks in place to provide torque when pushed in one direction but can be rotated freely when pulled in the reverse direction.
This simple ratchet tool mechanism allows the user to keep applying more torque to a nut or bolt, without having to lift and reposition the wrench after each rotation. This makes it much quicker and easier to completely tighten or loosen a given fastener, and greatly reduces strain on the user’s hands and wrists. It can also make it far more convenient to work in tight spaces, such as under cupboards or behind radiators and other fixtures.
The socket wrench is the simple handled tool with an inbuilt ratcheting mechanism, usually featuring a head design that allows for various sizes and shapes of socket to be added to one end. The sockets themselves are the differently sized drives that can be attached to the handle, ready to slip over and drive the various types of nuts and bolts you will be dealing with.
Socket sets typically feature an assortment of different drive shapes and sizes, designed to be swapped around on a wrench tool. The best socket sets will include a full range of standard drive shapes and sizes (both imperial and metric), with multiple pieces made to fit over any standard nut and bolt types. As such, buying a good quality wrench and socket set means you’ll rarely encounter a rotary fastener you cannot adjust.