There are three bidding strategies you can use in AdEspresso to determine how Facebook will bid for you in ad auctions. Select your bidding strategy in the Budget & Bidding step (4) of campaign creation.
Lowest cost (formerly automatic bid)
This strategy gets you the lowest possible cost for your selected optimization event and will use the whole budget. Lowest cost gets you the most conversions or impressions for example, at the best price, spending your budget as efficiently as possible.
Lowest cost with bid cap (formerly custom bid)
This strategy gets you the lowest possible cost for your selected optimization event up to the maximum limit you set as your bid cap. You are setting how much an optimization event is worth to you.
Target cost (formerly manual bid)
This strategy is available in External Website (with a Facebook pixel tracking conversions) and App Install campaign types. It lets you set a target cost per optimization event to keep your budget spend near that average (within a 10% range of your target) and stable throughout the campaign.