Use Issues for Requests and Activities for Tasks. An Activity is something that is done to resolve an Issue.
The Requests Issues library contains the issues available in the Create Request guided process. When applications are installed, any accompanying issues are added to the library and marked to display in the Issue list at the appropriate times.
Activities are the most important information stored in a task. An activity is the action performed on an asset. The activity may relate to maintenance, construction, inspection, or administrative actions.
For example, a request is submitted with and issue of graffitti. To fix the request a task of paint is created.