Need membership access explained

I would like to make sure that I am setting up acess in the members levels properly. for example Articles Delete means thy can only delete their article.

blog posts delete any post mean they can delete ANY post.  blog posts comments delete and edit do they delete and edit ANY comment or their own?  I see that some levels will allow you to edit only your own but what about those that does not explain? I would not want go give someone access to edit, or delete anything that is not theirs.

Can someone explain?

They really need to better explain these permissions.

its really important to have your own standard, premium, membership so you can test it....i have locked people out of things i didn't intend to because I misunderstood the settings so its good to have different accounts you can use for testing.