What is Unity Gain ?

What is the meaning of “UNITY GAIN ?” The Tram has a gain of 2.5 on UHF and on VHF it has a “Unity Gain” Could someone explain what is meant by the term "unity gain ?
Thanks in advance.

The term Unity Gain means that your input and output are the same, or in unity. For instance, in audio, if your input is 1 dB and your output is 1 dB, you have unity gain. In the case of the Tram antenna, it neither adds or decreases gain on VHF. Hence, it has unity gain on VHF.