A batch of standard tiles will have a great number of small differences between each tile. No two individual tiles are exactly alike; there will be many innumerable imperfections. On their own these imperfections are almost hard to notice. But the cumulative effect over a floor has to be compensated for.
Tiles are usually laid with 2-3mm of grout between them. This space between tiles compensates for their slight irregularity. The overall effect is a neat looking and well-spaced floor.
Regular tiles cannot be laid without space between them. The slight irregularity of the tiles will prevent them from fitting together perfectly. Gaps and irregular spacing will occur.
An exception to this is rectified tiles. These have had their edges mechanically trimmed, making them very close to uniform and perfect. This allows the tiles to fit together very neatly.
In practice rectified tiles still have grout lines, but they are much narrower than the grout lines of other types of tiles. This gives a seamless look to the floor or wall. With rectified stone or marble tiles the results can look like a solid stone or marble surface.
Kitchens can be decorated with rectified tiles to give a stylish seamless look, with walls or floors looking like solid stone or marble surfaces.
Rectified tiles are ideal for seamless wall surfaces. This is especially effective if the grout is the same colour as the tile.
Rectified tiles do take longer to install, requiring finer spacing, but the smooth and pleasing results are often considered worth the effort.