What is the difference between common and duplicate content?

Hi BHM fellows :3

I have blog related to money making scheme...
I always write my every content by myself and its readability is good as well.

Recently i've tried copyscape siteliner and it says,

99% common content
1% unique content
0% duplicate content


Is it too bad?

i am not sure how to answer your question. if you write your content manually, i don't think you will get 99% common

I believe common is where it is similar to others but not completely copied. However I could be mistaken.