Projected Start/End Dates vs Target Start/End Dates

[Thayne Munson]

I am setting up Plans in AR sourced by my Jira boards.  In Jira, I have been using Projected Start/End date fields for planning.  In AR, it appears that Target Start/End date fields is the default for planning timelines.  Is there a reason Jira/AR support both Projected and Target fields when they seem to accomplish the same function?  Or do I just choose one and run with it?  Thanks. 

[Thayne Munson]

After further review it does appear that AR will set the Target Start/End dates using the associated Sprint dates if the Target dates are not provided.  I assume this is the advantage of using Target vs Projected dates.