The conversions selection represents total conversions across all actions that you have chosen to include in the optimization. This could be website purchases, app downloads, phone calls, etc.
Conversions / All Conversions:
All conversions combine the Conversions column and any conversion actions that you’ve chosen not to include in Conversions column.
Click Assisted Conversions:
Assist Clicks can be defined as the total number of clicks a keyword received prior to a conversion, excluding the last click.
Phone Calls represent the number of valid calls received because of users clicking on a phone number or manually dialing the Google forwarding phone number displayed in an ad shown on any device.
Mobile Clicks to Call:
This is the number of clicks on your phone number when your ad is shown on a mobile device. This includes clicks on either a phone number in your ad text (in the US and UK) or on a call extension.