Target start: Planned start date when a team will start working on the issue. Used for Advanced Roadmaps plans.
Target end:Planned end date when a team will complete the work on the issue.Used for Advanced Roadmaps plans.
Baseline start date: Read only field. Used to indicate original planned start date, will be set automatically when for first time target start is set. Applicable for issue type Epic, Story, Enable Story, Task, Bug, Defect, Spike, Change request.
Baseline end date: Read only field. Used to indicate original planned end date, will be set automatically when for first time target end is set. Applicable for issue type Epic, Story, Enable Story, Task, Bug, Defect, Spike, Change request.