Adjusting volume

I’m mixing two tracks and want to adjust the volume of one of them. I’ve been told the sliding volume bar on the left side only adjusts the volume in Audacity itself, and not when you output it. Is this true? If so, how do I adjust the volume of one track and have it maintain that relative volume after the project is outputted?

I use Windows 10 Audacity version 2.3.2

I’ve been told the sliding volume bar on the left side only adjusts the volume in Audacity itself, and not when you output it. Is this true?

I guess you haven’t tried it?

You can also use the Amplify effect. If you want to reduce the volume (attenuate instead of amplify) enter a negative dB value.