Firstly let's look at wall tiles. Almost all wall tiles are glazed and can be either mono-cottura (once fired) or bi-cottura (twice fired). It makes little difference to the end user, providing the tiles are first grade. Watch out for some unscrupulous merchants who will buy second grade tiles and sell them to you as first grade. Always buy from a large reputable store with a good reputation to uphold.

Floor Tiles. These are much more complicated. The main categories for manufacture are pressed - extruded - stone.

Pressed Tiles are the most common and can be either mono-cottura or bi-cottura. Usually mono-cottura are fired at a higher temperature and therefore the base or biscuit is stronger. This will not make any difference to how the glaze lasts, but it will make the tile more impact resistant.

Bi-cottura tiles however can be produced with finer and more decorative glazes.
The important thing however is to ensure that the tile is wear rated correctly for your job.

Another category of pressed tile is the fully vitrified, or porcelain tile. These are extremely strong and good brands are almost non porous. They are often used for shopping centers and malls but are also excellent for domestic use.

Note… Some manufacturers put a clear glaze or seal over their fully vitrified tiles. This simply makes them a high quality glazed tile. This glaze can wear in some circumstances.

Extruded Tiles are often called quarry tiles. They are made from wet clay that is extruded into shape, then fired. This can result in tiles that are less dimensionally consistent than pressed tiles. Quarry tiles are often used outside or where a rustic effect is wanted.

Stone Tiles can be slate, sandstone, granite or some other stone. With the exception of granite, all are porous. Be aware that these tiles are pieces of stone. They may be sealed, but don't expect that seal to be as effective as glaze on a ceramic tile. It cannot be. Once you accept the limitations of stone, it can be an excellent product, but do not expect it to be something it is not. Granite is very hard and has low porosity, some of it approaching the quality of a vitrified tile, but it is still stone and must be treated as such. It is also very expensive.

What else?

Shade Variation. As with most products, tiles will vary in colour from batch to batch. This means you need to ensure that you buy all you need at one time. It also means that if you are buying large quantities, you need to ensure that you are being given all the one batch. There is nothing worse than having just laid most of your floor only to discover that the rest is the wrong batch. Shade variation is also the reason that you need to return any tiles that you have left over, promptly. Most merchants are prepared to accept returns on current stock shades but do not accept returns which don't match what they are currently selling.

Security. Many small shops keep very little stock. They buy in from a variety of wholesalers. This means that is anything goes wrong, you only have a wholesaler to go to. By dealing with a large reputable tile group such as Sogo Vitrified Tiles you have the reassurance of dealing with a company who has an India wide reputation to protect.