Try to understand Subscription Period

I had read the docs about Subscrition but still can’t understand fully.
So here I hope that someone can give clearer explanation.

There are Subscription Start Date [1], Trial Period Start Date [2], and Current Invoice Start Date [3]. What are their timeline?

Is it:



or else?

Because when there is Trial, the invoice start and end dates are the same with the trial.

Could the Trial be inside the Subscription period? like:
if so, how is the invoice period then?

What I try to understand is more on the logical of it, not the technical.
Thanks before for any explanation.

Can anyone please explain this?
Because in the docs there is no explanation regarding the periods.
Thank you