Fit View: Adjusts the window size to fit the image area. Effective especially when the image size and/or zoom level is such that the image is smaller than the workspace.
Zoom to Fit: Adjusts the zoom level and size of the window so that the image is displayed full occupying the largest area available within the workspace.
Zoom To Optimal Fit: Adjusts the zoom level of the image to fit optimally the available area.
Zoom 1:1: Sets the zoom level to 100%.