Viewpoint
The menu Navigation Gizmo or the following hotkeys:
lets you align the viewing direction to a specific axis. This can also be done using the- Top
Numpad7
- Front
Numpad1
- Right
Numpad3
- Bottom
Ctrl-Numpad7
- Back
Ctrl-Numpad1
- Left
Ctrl-Numpad3
The above hotkeys align the view to a global (world) axis. You can also align to a local axis of the selected item by additionally holding Shift. This way, you can for example view any mesh face head-on, no matter how it’s oriented. (To get out of this local viewpoint, simply align to a global axis again.)
The view can also be aligned by holding Alt-MMB and dragging the mouse in a certain direction.