What Azure DevOps work item types do you know?

The interpretation of what each work item type is used for differs between different companies but in general, the following definitions could be used:

• Product Backlog Item (PBI) - PBI defines what is to be done and how
• Task - task is a child of PBI and defines what exactly needs to be done in order to finish the PBI. One PBI can have multiple Tasks. As an example one task could be for Analysis, one task for Backend Development, one task for Frontend Development, one task for Testing.
• Epic - Epic item is a very large user story that is later broken down into smaller user stories/PBIs. Epic is very general and not very well defined functionality in the program. User story tends to express what a user wants to do: "As a manager I want to see the column xyz in the order grid so I can evaluate abc."
• Feature - A Feature item contains a description of a functionality that is to be built. A feature can be linked to PBIs. Think of a feature more in a product development standpoint ("This is what will be written in sales materials") than in a technical standpoint.
• Bug - Bug item describes an identified issue in the system together with description, steps to reproduce and other details that help developers to fix the reported bug.
• Incident - Incident item describes a potential issue reported by a user of the system. After the analysis is done, it can be found out that the incident is just a false positive or that there really is an issue in the system and in such case the bug is created.
• Test case - Test case is used for defining test steps that are to be done in order to test certain functionality.