You should really read more about OpenGL or General Graphics. Check what a Orthographic projection is : )
Your view will be the amount of the world you want to see in your screen, a rectangle..
If you want really independent screens within your screen, use render targets, or scissor test, or even multiple viewports.
But for an interface, its way simpler:
One sf::View for the world position and another sf::View for the default screen(normally equals the resolution)
Activate WorldView
-> Draw World
Activate DefaultView
-> Draw Interface
Because you render the interface relative to the origin (0,0) of the world, you activate the defaultview, so you get it rendered always the same independtly from where your world view is in the moment : )
All the change you make is into worldview, to pan and zoom, to see different objects, easy enough : )
Notice this way the views always fit the screen, its normal : )
Hope it helps