You can argue all you want about whether or not to go with ceramic or porcelain tile, but the bottom line is that if you're indoors it probably doesn't matter all that much. In fact, if you simplify it down to basics then porcelain is really just very dense ceramic tile. All ceramic tiles are made up of the same stuff: clay, quartz (ferrous sand) materials, and water. Tiles are formed and then "fired" to high temperatures in a kiln (oven). The clay used in porcelain tile is more refined and it is fired at a higher temperature which gives it its added density. The advantage, of course, is that this extra density makes it harder to permeate, rendering it excellent for outdoor use or where dirt and moisture may be present and cause staining on ceramic tile.

Most ceramic tile is glazed with a baked-on surface coating. Glazed tiles can be high-gloss, matte, or even come in an abrasive slip-resistant finish. They come in decorative styles and can be patterned or have a custom-painted design. It's important to note that the glaze only exists as a top layer coating, so if the tile chips you'll see the natural ceramic or porcelain color underneath. 

While all this may seem confusing, if you're tiling indoors then you actually should care more about the general PEI (or hardness) factor of the tile than anything else (excepting, perhaps the color or style of the tile). While there are indeed other factors to consider, let's take a quick look at PEI.

PEI (Porcelain Enamel Institute) ratings range from 0 to 5 and reflect the intended use for the tile. You could simplify it and say that the higher the number, the more scratch-resistant and shatter resistant the tile is going to be. For example, you would never put wall tile with a PEI rating of 0 on the floor. It will likely scratch and/or crack under use. PEI 2 tile can be used on floors, but only where there is a low amount of foot traffic. Most residential floor tile sold in stores is rated PEI 3 or 4. If you're going commercial, then PEI 5 tile is the way to go as it is designed for abusive and extra heavy foot traffic. Here is a quick run-down of the PEI scale:

• Class 0 - No Foot Traffic
  Wall tile only and should not be used on floors.

• Class 1 - Very light traffic
  Very low foot traffic, bare or stocking feet only. (Master bath, spa bathroom).

• Class 2 - Light Traffic
  Slipper or soft-soled shoes. Second level main bathroom areas, bedrooms.

• Class 3 - Light to Moderate Traffic
  Any residential area with the possible exception of some entries and kitchens if extremely heavy or abrasive traffic is anticipated.

• Class 4 - Moderate to Heavy Traffic
  High foot traffic, areas where abrasive or outside dirt could be tracked. Residential entry, kitchen, balcony, and countertop.

• Class 5 - Heavy Traffic
  Suggested for residential, commercial and institutional floor subjected to heavy traffic.

Whether you select ceramic or porcelain, glazed or unglazed, you'll find that both offer almost limitless sizes and shapes to meet your needs in nearly any circumstance or application. Just match the tile to the application and then select the look that's perfect for your home or office project. Enjoy!