frequency - QAM modulation - how data in different frequencies are laid out?

I know that QAM modulation uses a change in phase and amplitude to send data. But We use a series of frequency spaces as bandwidth to send data.

However, we know that different frequencies oscillate differently. So, if we modulate data using several frequency spaces together, how are data laid out?

Is it that size of data in each frequency is different? Or is it something different?

Thanks.