When in Edit mode, the right side of the screen is sort of a preview. How to turn it off?

[Art Coleman]

Very new to creating pages in Confluence.

I've created several pages over the past few days.

One of them, when I go in to Edit mode, has the right half the screen taken up by what looks like a preview of part of the page I am editing.  Meanwhile the edit area is just the left half of the screen.  If edit changes are made on the left side to what is shown on the right side. the side does not update (so not actually a preview).  Going into Preview, the right is normal, and the page is full width.  Back to Edit and the same (un-updated) text is on the right side.

What did I turn on?
How did I turn it on?
How do I turn it off?

     advTHANKSance   

[repi]

Please visualize it. Can't understand the question!