Bid adjustment: Definition
A percentage increase or decrease in your bids. A bid adjustment allows you to show your ads more or less frequently based on where, when and how people search.
You can also adjust your bids based on how your ads perform, which helps to improve your return on investment (ROI).
Your spending on individual clicks may vary as your bids increase or decrease according to the adjustments that you've set, but your overall daily budget won't change.