Activity relates to all the tasks under a particular source ( for example Source type is the project management and selecting a project under a source and then creating an activity of that specific source)
1) Add activity:
Task--> Add Activity
Choose the source type: whether project management, campaign, ticketing system etc.
Source: Choosing the individual source of that source type. For example: source type project management and name of the source is the name of the project where you will create the activity
Title: Name of the activity
After completing the information, click on the save to finish creating new activity
2) Activity List:
Showing the list of all the activities that are being created under task management solution. It also shows the detail information under a specific activity. Also in the activity list you can create new activity by clicking on the "+" icon as well as edit any activity. The screenshot is provided below for better understanding.