Decibel (dB)
Ratio between two signal levels
Makes it much simpler to express and calculate power gain or loss
Tens and threes of RF mathematics
A gain of 3 dB (+3 dB) means the signal is two times bigger (twice the power)
A gain of 10 dB (+10 dB) means the signal is 10 times bigger (10 times the power)
The same applies for loss