Roughly what is the difference between "Copy Number 21Q4 Public" and "Expression 21Q4 Public"

In general I am looking for protein expression levels of receptors in several cell lines. I know that Expression 21Q4 Public reffers to mRNA levels and I was wondering what the “Copy Number 21Q4 Public” is, just in case it is more accurate for the purpose I need it.

Thank you very much for your time and all your help.

“Expression 21Q4 Public” provides the mRNA expression level data for a gene across all available cell lines, whereas the “Copy Number 21Q4 Public” dataset provides the log-fold change of the relative DNA copy numbers of a gene across cell lines. It sounds like the Expression dataset would be more appropriate for what you’re looking for.