As installed there are a number of defined Issue types supplied. These may or may not be suitable for the particular installation.
One can choose to delete the supplied values, however it is probably easier to just 'unpublish' them and create any new values that are desired.
Issue types are associated with specific 'projects' so it is possible to have different types for each individual 'project; if it is so desired.
If published the issue types will be visible in the site front end for a selected 'project'.
It seems likely that one would desire their own set of 'issue types', what these would be would depend upon the specific site requirements. [Current types such as 'defect' 'documentation' etc., may not be applicable.]
Remember to specific the component option for the required 'default issue type' that is assigned if the user chooses not to select one of those presented or if the issue type is not displayed to the user.