Sometimes the nicest interior can have a horrendous view outside the window or door.
Or you want to de-emphasize the proximity of the neighbor's house is, as with the shot on the left.
Burn it. The simplest thing is to expose so that bright daylight outside burns out enough detail of whatever's out there.
This is very easy to accomplish... just leave the shutter open long enough.
Unfortunately, you'll still have to get a good exposure indoors and that can involve some compromise.
You may elect to have overexposed highlights inside the room (typically the lamps) in order to guarantee burnout of the outdoor ugliness.
This is a good case for bracketing exposures.
It might be a good situation for shooting when it's bright outside.
Shade it. Sheer curtains can obscure the outdoor problem while letting in plenty of light.
Various other blinds and translucent shades can also work, though I avoid drawing shades fully closed.
Watch out for blinds with defects (bent slats) and dirt, or that cast unwanted shadow patterns.
Diffuse it. There are translucent films you can apply to windows so that details outside are blocked.
If using the permanent type (for bathroom privacy), be sure you'll be able to remove the film afterwards.
You can also hang a large photo diffuser outside a problem window as long as it covers the unshaded part of the window.
