Conversion Tracking

Conversion tracking is any method of documenting conversions. In order to use maximize conversions bidding, which unlocks the awesome ability to bid above $2 for a click, the method of conversion tracking must be something that can be understood by your AdWords account. There are many different ways to track conversions, so make sure you choose a method that can import information to your AdWords account and then correctly link your conversion tracking system before you switch your campaign’s bid type to maximize conversions bidding.

Read Google’s definition.