What is the difference between standard “ceramic” tiles and porcelain tiles?

[Dave]

Tile terminology can be confusing. Most types of tiles that are made from clay or a mixture of clay and other materials, then kiln-fired, are considered to be a part of the larger classification called “Ceramic Tiles”. These tiles can be split into two groups, porcelain tiles and non-porcelain tiles. These non-porcelain tiles are frequently referred to as ceramic tiles by themselves, separate from porcelain tiles.
“Ceramic” or non-porcelain tiles are generally made from red or white clay fired in a kiln. They are almost always finished with a durable glaze which carries the color and pattern. These tiles are used in both wall tile and floor tile applications, are softer and easier to cut than porcelain, and usually carry a PEI 0 to 3 rating. Non-porcelain ceramic tiles are usually suitable for very light to moderate traffic and generally have a relatively high water absorption rating making them less frost resistant and they are more prone to wear and chipping than porcelain tiles.
Porcelain tile is a tile that is generally made by the dust pressed method from porcelain clays which result in a tile that is dense, impervious, fine grained and smooth, with a sharply formed face. Porcelain tiles usually have a much lower water absorption rate (less than 0.5%) than non-porcelain tiles making them frost resistant or frost-proof. Glazed porcelain tiles are much harder and more wear and damage resistant than non-porcelain ceramic tiles, making them suitable for any application from light traffic to the heaviest residential and light commercial traffic. Full body porcelain tiles carry the color and pattern through the entire thickness of the tile making them virtually impervious to wear and are suitable for any application from residential to the highest traffic commercial or industrial applications. Porcelain tiles are available in matte, unglazed or a high polished finish.