|IR (stands for ImageReady) has to be installed on your computer during the typical Photoshop installation.|
Run it now independently or switch to it from PS (Photoshop) either by clicking on Jump to ImageReady button at the bottom of PS' Toolbox or using [Ctrl+Shift+M] shortcut. Similarly, you can switch from IR back to PS. The two applications are designed for joint work.
As you can see that the IR interface is very similar to that of PS: the same workarea with the Toolbox, Options bar and several other palettes. However you can note a few differences.
1. Image window has 4 tabs allowing us to view the original image and / or previews of Web optimized versions (screenshot).
2. There appear some new palettes.
3. A few different buttons on the Toolbox.
4. One new pull-down menu (Slice).
And lots of minor differences in pull-down and context menus, shortcuts, palettes, etc.