Try to record at the highest possible level without the signal distorting.
The noise floor is the measurement of all volume of all all the unwanted noise in a recording. No accurate measurement can be taken below the noise floor, so the smallest measurement that can be reliably taken is above the noise floor. The lower the noise floor the better because the larger the usable dynamic range. There is a much higher noise-floor in analogue recording, meaning a smaller available dynamic range, so a compressor is often used to lift as much information as possible clear of the noise floor.
An analogue recording has a higher noise floor.