We cannot expect physically manufactured objects like tiles to be perfect, or even perfectly identical. Any batch of tiles will have small but significant inconsistencies between individual tiles. These will become noticeable if the tiles are put closely together. Some tiles will be fractionally larger, some slightly irregular in shape. The means tiles cannot be joined edge to edge, because the irregularities will accumulate over the space of a floor. The result will be a tiled floor that is noticeably uneven and asymmetrical.
Usually the irregularities of tiles are absorbed by the space between them, the space filled by grout. Slight size and shape differences are not noticeable when the tiles are separated by a few millimetres.
Rectified tiles are different to standard tiles. These tiles are mechanically trimmed so that a batch of tiles will be extremely uniform.
These rectified tiles will still require grout line between them, but the grout space can be much tighter. This allows an almost seamless surface, looking like solid stone or marble. This type of wall is especially effective is the small grout spaces are fill with a colour that is identical to the tiles.
Rectified tiles can be used to create a very different bathroom décor. Rectified tiles can look like stone or marble, which is a rather elegant look. The rest of the bathroom décor should be chosen to match this style.