Neo can work with a number of sensors, and which you use depends on your use of the room.
1. The sensor built in to the neoStat can measure the temperature at the thermostat
2. Remote Thimble air sensor - can measure the temperature remote from the thermostat
3. The floor sensor can measure the floor surface and prevent overheating.
4. Option 2&3 together. Software option can select this.
This can measure the air and use the floor sensor to limit the max temperature of the floor to protect the floor surface.
These sensor modes in Neo enable you to control the temperature at the point important to you. For example it makes sense to control the floor temperature in a kitchen or shower room, so that the floor tiles are warm to walk on.