For all the items there is pre-defined prefix. It is currently not configurable.

Following list explains prefix types

In views where we there is data from multiple projects you will have project short name or key appended before the ID. For example, if you create first project, probably the default key created is "project1" (which you can change at any time by going to project settings)

This default design, helps to identify quickly, what sort of items user is looking at, for example, at Sprint board, where you have both issues and tasks under user stories.