I'm new to Illustrator and I'm making an illustration, the problem is when I moved the red rectangle, the surrounding border seems to stay there, I can't select it and it does not move or remove, and when I click on the eye button beside layers, I figure out it doesn't belong to any layer. I searched about it and I know it's not my art board. What can it be and how can I remove it?
I hope it's not a redundant post.