Floor heaters can include baseboard heaters, simple space heaters, foot warming pads, central heat and more. The term floor heater is really broad so it can be just about anything really. If you are looking for a built in heater, then you are moreso looking for a wall heater. Baseboard heaters rest at the bottom of the baseboard and the floor and are great floor heaters.
Foot warmer pads are not really heaters, but they are heaters too, aren't they? They'll keep your feet warm in the winter time and that is important. People also use these for their dogs sometimes to keep them warm or other pets (we don't recommend it but people do it). Certainly, foot warmers and the like to keep just about anything warm that you need. However, you'll still want to keep some things cold (like beer). If you're not sure how big of a heater you need, or how many, then the next question is - how big of an area do you need to heat? If heating one room or two small rooms, one or two small electric space heaters are fine. A bigger area like a hall, you'll need a mixture of heaters or a few large units. Central heat is usually best in these situations.