Cucumber

Cucumber Objects

Task
A task class is used to implement a single, reusable workflow within your SIT. A task does this by combining a series of action classes together, possibly (but not required) with additional logic/checks.

Action:
Actions are only expected to be called within tasks and should be considered private for the module that authored them. Actions should always be hidden behind tasks and not be visible for developers outside a particular module.

The TaskData interface represents the input and output data a task needs to perform its implementation.
The TaskDefinition interface represents the implementation of a task and takes in a specific implementation of TaskData to get its input and know what it should return.

Reference:
http://3qilabs.com/how-does-cucumber-automated-testing-work/
https://github.wdf.sap.corp/pages/SF-Automation/Documentation/documents/ADF%20v2/2.%20Comprehensive%20Guide/3.%20Journey%20Pattern/