Optimise for clicks: Show ads expected to provide more clicks
Ideal setting for most advertisers.
Optimise for conversions: Show ads expected to provide more conversions
Ideal setting if you use AdWords or Google Analytics conversion tracking.
Unavailable because conversion tracking is not set up. Set up conversion tracking.
Rotate evenly: Show ads more evenly for at least 90 days, then optimise
May be appropriate if you optimise ads using your own data
Rotate indefinitely: Show lower performing ads more evenly with higher performing ads and do not optimise
Not recommended for most advertisers.