A bidding strategy in digital advertising is the method used by advertisers to determine how much they are willing to pay for ad placements and how they allocate their budget to achieve their advertising goals. 

It involves setting bids for specific actions such as clicks, impressions, or conversions and may include manual bidding, automated bidding, or a combination of both.

Bidding strategies are tailored to campaign objectives, target audience, and budget constraints to maximize return on investment (ROI) and achieve desired outcomes such as increased website traffic, leads, or sales.