The wood floor can be installed mainly in two ways: glued-down o floating.
It is the most common solution, it can be installed on new floor slabs, on old tiles and even with underfloor heating.
You must first apply a layer of glue and then install the flooring, the adherence is almost immediate (depending on the type of glue), you’ll can walk over it the very next day.
In the case of existing tiles it is necessary to scratch them first (I prefer this technique to using acid) in order to make their surface porous and clean enough for the glued installation.
It’s a less used solution. You must first extend a subfloor (a polyethylene foam laminated sheet with a high density polyethylene film) and then place the new wooden floor over it, taking care of pasting only the joints (to give more stability). No other measures are needed in case of both, new or old floor.
Which solution is best?
The answers is, as almost always, it depends. If you have underfloor heating you are forced to choose a glued installation, otherwise the floating installation allows you to return the floor to its initial state without damaging the existing tiles.
The main defect (but it’s subjective) for floating foor is that the floor is slightly more noisy when walked on. The main advantage is that, if you’ll move house you can always remove it and take it with you.