Chrome plating, often referred to simply as chrome, is a technique of electroplating

Electroplating

Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...

 a thin layer of chromium

Chromium

Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...

 onto a metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 object. The chromed layer can be decorative, provide corrosion

Corrosion

Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 resistance, ease cleaning procedures, or increase surface hardness.
A component to be chrome plated will generally go through these different stages:

• degreasing
  Degreasing
  Degreasing often called Defatting, is a term used to describe the removal of fatty acids from an object. In culinary science, the word degreasing refers to various methods which are used to reduce the fat content of a meal. This term can be used to categorize procedures that reduce the fat content...
  
   to remove heavy soiling;
• manual cleaning to remove all residual traces of dirt and surface impurities;
• various pretreatments depending on the substrate;
• placement into the chrome plating vat, where it is allowed to warm to solution temperature; and
• application of plating current, under which the component is left for the required time to attain thickness.

There are many variations to this process depending on the type of substrate being plated upon.