Managing keywords/description

[Mike_in_Montana]

Hello,  I'm new here.  I don't quite understand how the 5 different categories to describe the image are used or its importance.  I understand the need for keywords, and perhaps the difference between essential and main keywords...  But, how does the caption, comprehensive keywords, and description come into play?  Because of my lack of understanding on these, I find myself essentially repeating the keywords entered elsewhere.  What is the most efficient way to enter these without duplicating everything?  Any other tips regarding keyword entry?

 

Thanks much!