Short version: A bid strategy is the way an ad platform sets or manages bids to reach a campaign goal.
In paid advertising, bids influence how often an ad enters auctions, where it can appear, and what the advertiser may pay for clicks, impressions, conversions, or conversion value. A manual strategy leaves more bid control to the advertiser, while automated strategies use platform signals to adjust bids toward goals such as clicks, conversions, target CPA, target ROAS, or impression share.
The right bid strategy depends on the campaign objective, tracking quality, budget, conversion volume, and business economics. A campaign optimized for cheap traffic can bring the wrong visitors if the real goal is sales. A conversion-based strategy can struggle if there is not enough reliable conversion data. Bid strategy should therefore be chosen with measurement, budget, and landing page quality in mind.
Related terms: campaign objective, CPC, CPA, and ROAS.