RF loss of signal

The further you are from a wireless broadcasting device (here we are usually dealing with wireless routers and Bluetooth) the less signal you get (though the signal can also be reduced by [for example] walls).

This can be useful as it means that it is possible to use devices on the same radio frequencies in the same locality so long as they are at sufficient distance from each other that the radio signals don't clash.

A good example is Bluetooth which is designed only to reach a few metres -- in practical terms it may only have to reach from a phone earpiece to the phone.

That means that in a restaurant, for example, several people could be using Bluetooth enabled phones without causing problems for each other.