The Walk tool lets you to move your viewpoint in the viewing area by moving your mouse around, as if you were walking in the store. (Keyboard shortcut W)
You can use your mouse:
Or you can use the keyboard:
Select any other tool to exit Walk tool.
Note: As soon as you start a new walk with this tool, the viewpoint is automatically relocated to match an average human eye level and sight angle.
Tip: you may want to widen the FOV for a more lifelike experience when walking (see Field of View).
Tip: this tool is also available in the Navigation menu and Context menu > Navigation.