Radio Transmission - Power/Strengh of the signal

(In general) The strengh (power) of a signal is the amplitude of the waveform (in Watt).
(e.g. GSM 2 watts, 802.11 30 milliwatts)

The power of a signal decrease in its medium (attenuation (variable following medium and the frequency of the signal)),

The amount of power added or decreased is expressed in decibels (dB) (e.g. a connector can decrease the amount of power),
Noise is also there and the signal is subject to that. The metric is the SNR (signal to noise ratio).