A chronograph watch is a watch that has additional features to a watch that just tells the time and perhaps the date; it is a complicated watch, this is because the extra features are called complications. These additional features are often some type of stopwatch timing ability that is facilitated by the presence of sub dials on the main watch face.

The extra functions of chronograph watches are operated with push buttons located next to the winder, depending on the design and manufacturer there maybe between one and four of these push buttons. These complications or extra functions may number as high as ten or more, but these are usually on very expensive mechanical watches. These types of chronograph wristwatches are more about showing off the skills of the designers and craftsmen who build them, rather than about making functions that anyone would want to use very much. Also these types of chronograph watches are only built in limited numbers for avid watch collectors and rich ones at that, they can cost literally millions of dollars!

Digital watches have made it possible for even cheap chronograph watches to have many functions and be accurate to a few second per month, but chronograph watches are often bought as much for their appearance as for their function, or at least it becomes a secondary consideration after style.

Although chronograph watches may be a chronometers the two terms should not be confused as they are not interchangeable. A chronometer could be a watch, although not necessarily as it could be any timepiece, that has design features that make it very accurate at keeping time regardless of external conditions.

Getting greater accuracy for clocks and watches has been a challenge since the first mechanical clocks were produced in the 16th century, then accuracy was so poor, errors of plus or minus hours per day made them more novelty items than timekeepers. It wasn't until 1657 when the balance spring was added to the balance wheel that things took a big leap forward with regard to accuracy.

With mechanical parts made of metal, temperature changes were a particular problem, as changes caused by expansion and contraction of the parts, particularly the balance wheel, caused the mechanism to run faster or slower. To overcome these problems designs were changed and in the mechanism itself accuracy was improved by the use of metals that were stable through a range of temperatures. You will also find that some chronometers have protection against the effect of magnetic fields.

The use of bi-metallic balance springs, where metals having two different coefficients of thermal expansion are used to keep the force of the spring even through a range of temperatures, was pioneered by John Harrison. Harrison was the English clockmaker whose life's work was the development of the first real marine chronometer. John Harrison's drive to produce a chronometer was the problem of "longitude" that made navigation at sea so difficult and the prize to solve it, as in the film of that name made in the year 2000.

So basically any type of watch may be a chronometer, but a chronograph watch isn't always a chronometer, but they could be one and the same thing!