For example, low fire tiles or tiles that have only been through a bisque firing are generally less expensive but not nearly as durable as high fired tiles. Even if the tile has been glazed, it may still have only gone through one firing and very possibly only a low firing so the fact of it being glossy and colorful is no indication that the tile has the durability of a high-fired tile. Greenware - ceramics that has dried but not been fired, can be glazed with a low fire glaze and fired to a comparatively low temperature.
Such a cermic tile would not be suitable for certain applications. For example if you intend to use the tile for a backsplash, counter top or tabletop you will need a very durable tile that will hold up to frequent cleaning and in the case of a countertop or tabletop, some hard use too. Stoneware clays are the most suitable for this sort of use. Stoneware is normally fired to about cone 6 (around 2200 degrees F) and is very strong.
But in your inquiry, don't stop with what kind of clay the tiles are made from. Glazes vary enormously and even so-called 'food-safe' glazes can leach out chemicals, stain and lose their color. Many manufactured tiles are poorly made and will not hold up to the uses they are marketed for. Of course, there are many quite excellent manufactured tiles too so you need to inquire to be sure. That information however may or not be readily available.
The kind of ornamentation of the ceramic tile is important too. For a ceramic countertop or tabletop, the tiles should be flat. For a backsplash the tiles can have low relief but high relief will be difficult to clean and is not generally advised.
Fireplaces, murals, mosaics and facades can be either flat, have low relief or high relief and low fire glazes are OK in these applications. Be careful though with areas that will get much use, such as around a fireplace where logs will be placed or fireplace tools will be used. Low fire tiles and glazes can crack or chip much more easily than stoneware and high fire glazes. Also, if it is an area that will require frequent cleaning, high relief may prove troublesome.
For ceramic walls in dry areas not subject to much physical contact most any type of tile and glaze is adequate. For wet areas flat tiles, low relief tiles or even high relief tiles can be used so long as they are not in a hazardous place that a body can inadvertently come into contact with them. A large frog leaping out from your shower wall at body height is probably not a good idea.
Obviously, porous tiles are not good for wet areas. So long as the tile is vitreous - has been fired to maturity such that the crystalline structure is unified - the tile or glaze is OK, however the joints between the tiles will need to be sealed. Again, the best bet here is a high fired stoneware tile with a dependable glaze.
Flooring presents other challenges, and opportunities. Clearly floor tiles must be durable so high fire stoneware is the best choice. Any kind of relief is not advised as uneven surfaces can be difficult to walk on, especially for the aged. An additional consideration with flooring tiles is slickness. A glossy glaze on a floor is not recommended. A heavily textured glaze or a matte glaze is best.
Outdoor use in cold climates demands high fired tiles and dependable glazes, especially if on horizontal surfaces. Low fire and even porous tiles can be used outdoors in cold climates if on or in a vertical surface. But you are still better off with a frost proof tile in cold climates.
Finally, there is the issue of a ceramic tile being food-safe. Many decorative ceramic art tiles are used as serving trays for a variety of hot and cold foods and it is important that these not leach out chemicals. Even a glaze said to be food-safe often is not. John Hesselberth and Ron Roy, in their book, Mastering Cone 6 Glazes demonstrate this by placing a lemon wedge on a 'food-safe' glazed piece of ceramics. Within hours the glaze is discolored from leaching out of the chemicals.
Unfortunately, the food-safeness of a glazed or handpainted ceramic tile is difficult to determine unless you can speak with the maker because of the fact that many glazes said to be food-safe are not. Which is one of the great advantages of handmade tiles - the ceramic artist can tell you if it is food-safe. Here at Handmade Ceramics and Fine Art Studios we make our own glazes based on the recipes tried and tested. If you can't find out whether your ceramic art tile is OK with food you're better off not using it for that purpose. Use it as a ceramic wall tile or if it is durable and mostly flat, for a trivet.