Percentage change
Percentage change is a move measured against where it started: the change in price, divided by the starting price, times 100.
The same dollar move means different things at different prices. A rise of $1,000 is 10% from 10,000 and only 1.25% from 80,000. Comparing moves in percentages, not dollars, is what a log chart does visually.
Learn more: linear or log chart.