Key event
The events that measure actions that are important to the success of your business are called "key events". A key event is an action that's counted when someone interacts with your ad or free product listing (for example, clicks a text ad or views a video ad) and then takes an action that you’ve defined as valuable to your business, such as an online purchase or a call to your business from a mobile phone. When someone triggers the key event by performing the action, it's recorded in Google Analytics and surfaced in your Google Analytics reports.
You can use the behavioral data from your key events to improve the user experience across your websites and apps.
Key event is an umbrella term which includes both conversions that come from ads and purchases that would come from free listings. This is also the naming for the setup which covers both.
Conversion
A conversion is an action used to measure the performance of your ad campaigns and optimize your bidding strategy. It covers clicks, purchases and every type of conversion which has been already defined as a conversion.
Conversions are specific to the context of ads. Unlike key events, conversions are eligible for bidding and reporting in Google Ads.
To create a conversion, identify a key event in Google Analytics that measures an important interaction. Then in Google Ads, create a new conversion based on this key event. After you create the conversion in Google Ads, the conversion data is shared between Google Ads and Google Analytics so you're viewing the same data across platforms.
Purchase
The total number of purchases coming from your products shown on Google.
- A “purchase” occurs when a customer, who clicked on a link to your site shown organically on Google Search, completes the buying process on your online store or app.
Simply looking at product images or clicking on links to product pages doesn't count as a purchase.
