As durable as ceramic is, by nature it is porous and needs a glaze applied to seal it.
Once a tile has been shaped and "fired", a glaze is applied and it is "fired" again.
NOTE: For flooring, it is highly recommended that an additional over-all application of sealant be applied to the entire floor after installation.
Although tiles can be slippery, by adding an "anti slip/skid" sealer (after tiles are installed and sealed with the glaze) will prevent any slipping, will not change the appearance of the tile and will be virtually unnoticeable.
We encourage you to visit ceramic tile flooring where you will find much more detailed, in-depth information about ceramic tiles
Sweeping and mopping on a regular basis will keep ceramic tile flooring looking like new.
If a tile needs replacing (a crack forms, etc.), all you need to do to replace it is loosen it with a puttying knife (or similar object) around the edges and lift it out, "mud" (with glue) a new tile and fit it into the vacant spot, apply the grout around it and let it dry. Once the grout has dried, seal the tile/area with ceramic glaze like the rest of the floor.
Periodically, the entire ceramic floor tiles will need another application of glaze sealer. The key is when the glaze is no longer visible to the eye. When the glaze has worn off the tiles, especially in higher traffic areas, it is time to apply another coat of the glaze sealer. Areas with low traffic, like along the wall, may not need to be re-glazed/sealed as often.
Prices vary, depending on where you live, but over all, ceramic tiles are relatively inexpensive compared to other types of flooring.
When buying your tiles, always buy from the same lot number and buy a sufficent amount of extras to allow for breakage during installation, or later for any necessary repairs.