To set two things side by side to see how they differ. Comparison needs a shared axis, and naming it is the method.
Latin comparare (to match, pair, liken), from com- (together) + par (equal); to set two things beside each other on the assumption they can be measured against one shared standard.
The setting of two things side by side to see how they differ. The comparison is only honest once the shared axis it runs on has been named.