What are the main characteristics of a wrist watch?

The components of a watch generally differ depending on the type of movement used, ie:

• Mechanical: these can be hand-wound or automatic watches. The automatic ones have the ability to fully charge themselves with the movements of the wearers hand.
• Analog: these are battery powered quartz watches with the classical approach of displaying time with hands on a dial.
• Digital quartz watches powered by battery and displaying the the passage of time in the form of numbers through the use of liquid crystals.

The watch case.
The case is the outer structure of the watch and the body in which the movement and features the watch are stored. It consists of the caseband, the back and the basel with the glass cover. The cases commonly have five different shapes: squared, rectangular, round, tonneau shaped and oval. The case can be made out of different materials such as precious metals like platinum, gold and silver or less valuable one like titanium or steel. It can also be gold plated.
The materials are described below: 1) The Platinum used for making watch cases is an alloy that contains 950 parts per 1000.
2) Gold: the precious metal that is most used for the manufacture of cases on luxury watches. The most valuable cases are those made of more than 750 parts per thousand, but in order to reduce costs without losing the right to call them "gold", some cases are also produced in alloys with 585 and 385 parts per thousand. The gold color of the case depends on the metal that is used in the alloy.
3) Titanium: is a space age metal that is proving increasingly attractive to the
production of watch cases for its high strength to weight ratio. It is
antimagnetic, does not provoke any allergies and does not corrode. It has a pearl-gray color and a smooth surface and its appearance changes with the light.
4) Gold Plating: in this case, the case is made out of brass and it is then
subjected to special treatments such as copper and nickel plating, needed to
ensure the adherence of the coatings obtained by dipping the case in a gold bath
that attaches to the substrate by electrolysis. The thickness of the coating is generally 10 or 20 microns (one micron equals 1 / 1000 mm). Another procedure, used more rarely because of its costs is lamination which establishes a thin gold foil on a sheet metal (or alloy) such as brass or steel.

Watch complecations and capabilities.

A complication is an extra function supported by a watch other than simple timekeeping thus containing movements and mechanisms prepared to perform those functions.
The most common are:

The chronograph: is a highly appreciated function; a chronograph watch also supports stopwatch capabilities alongside the normal timekeeping functionality.
The stopwatch is independent and does not interfere with the regular timekeeping.

Chronometer: This term indicates that the clock has passed stringent tests
regarding precision. Be careful not to confuse the term with the word chronograph stopwatch: they are two different things. A chronometer is a watch that has received a certificate which guarantees its accuracy and build quality and can be used to precisely calculate the longitude by means of astronavigation.

A repeater is a special watch function which acoustically indicates the hours, quarters and minutes. The mechanism is activated by a button or slide on the case and it strikes the number of hours. Repeators were generaly used to allow the time to be determined before the advent of phosphorescent materials. Watches with repeaters are now rare and very valuable.

The Tourbillon is a special mechanism designed in 1795 by Abhram Louis Breguet and subsequently patented in 1801, with the essential purpose of reducing errors caused by the uneven running of the watch balance wheel due to gravity or shocks. It consists of of a mobile structure that contains the elements of the escapement. This structure makes its own rotating motion within the watch movement. The tourbillon is a major complication for the wristwatch and represents an element of great value.

Water resistance
There are two general types of water resistant watches:

a) Impermeable: these are watches with cases that are penetrated by moisture and water. The status of water resistance for a watch should always be accompanied by a clear indication of the actual level of tightness of the case (usually shown in meters).
b) Waterproof: watches that are resistant to immersion at depth. Resistance is generally indicated in atmospheres (atm) on the back of the watch itself.