I recently wrote an article for the Disc Makers blog, Echoes - Insights For Independent Artists, called "What is the difference between loudness, volume and gain?" The main focus of the article is along the lines of my constant harangue about audio terminology and how its often confusing and sometimes overly technical jargon can make it difficult for regular people (i.e. NOT engineers or other techie types) to learn audio recording concepts. This particular time, I wanted to shed some light on the terms: gain, volume, loudness and levels.
Read the article here if you want to know more about this stuff: Recording Studio Difference Between Loudness, Volume And Gain