Google Adwords is Google's advertising platform that allows you to promote your product on Google’s search.You pay only when your customers click on your Ads. By adding a conversion tracker from Adwords to your shop, you can track and analyse customer behaviour.
You may refer to the following for more details:
Sign in to your Google Adwords account. Click on "Tools" -> "Conversions"
Select "Website" as the source of conversions you'd like to track.
Enter the name of your conversion action.
You can decide whether or not to put a value for each conversion.
Click "Save and continue".
Copy the conversion ID and the conversion label.
After setting up your conversion action in the Google Adwords account, go to your shop's admin panel.
Click "Shop Settings" -> "Tracker Settings" then add a Google Adwords tracker.
Pick the action that you want to track and paste the copied Google conversion ID and Google conversion label.
Don't forget to click "Add" to save the tracker!