Trigger campaign also known as trigger marketing or trigger based marketing, is an event based marketing strategy.
For example a campaign launched to solve occurrence of a problem like the weight loss issue.
These campaigns are launched to identify or bring about a change using certain triggers in peoples lives.
Triggers could be email notifications or text messages to inform users to take some action or alert them that they are missing out on something like they have left products in their cart and not checkout or the product will go out of stock.