A conversion occurs when a visitor clicks on your Ad and this leads to a desired user activity or behaviour you consider as desired example:
Newsletter signup Lead generation Purchase
Google provides 2 metrics to measure converions… 1-per-click and many-per-click
This helps us understand how many conversions have resulted from the number of clicks on your ads.
1-per-click conversion We count (1 per click) conversion when a ad click results in a conversion within 30 days. This means if more than 1 conversion occurs following single Ad Click , then only first conversion counts and conversions after the first conversion are not counted.
Many-per-click conversion We count (many per click) conversion when a ad click results in many conversions within 30 days. This means if more than 1 conversion occurs following single Ad Click , then all the conversions counts if within the 30 days.
Easy Example of … 1-Per-Click Conversions vs. Many-Per-Click Conversions:
Assume you have a conversion tag on feedback form thank you page and another on a Order confirmation or Thank you page. If a user clicks on one of your ads, fills feedback form and then decides to order a product and reaches the “Thank You” page, you in turn will receive:
Conversions (1-per-click): 1 Conversions (many-per-click): 2
By Sunil Datar Google+