Digital special effects (Visual Effects - VFX for short) don&t always have to be spectacular - not only in big Hollywood productions are the invisible VFX almost omnipresent, which are not the center of attention in a scene, but rather form the background and are perceived by the viewer as a matter of course as real.
The linked clip shows very nicely on a number of examples of well-known films, for which purposes computer-generated images are inconspicuously used in films. VFX play an extremely important role nowadays, for example, to replace classic sets with backgrounds - instead of constructing complex facades, streets are simply simulated digitally or real views digitally supplemented.
For Marvel&s "The Avengers" (2012), for example, more than 20 blocks of Manhattan have already been photographed and digitally modeled so that the fight of the superheroes against the alien invaders can take place in realistically simulated New York. Mass scenes also increasingly consist of calculated or digitally multiplied extras. Most of these hidden effects are only visible in 
VFX-Breakdowns, so unobtrusively they are integrated into most scenes.
The quality of digitally generated objects has been so good for some time that they can increasingly replace real images - and they are constantly being improved and made more affordable. This means that even in films without a mega-budget or even in TV series, complex sets and equipment can be used, which enhance the productions enormously, but would have been unaffordable in reality - especially in science fiction, fantasy or history films, of course. But even everyday settings such as street scenes can be filmed easily and cheaply in the studio using a green screen instead of shooting outside on location.
A special category are the recent simulations of actors, especially their faces, which allow the resurrection of dead actors (such as Carrie Fisher / Princess Leia in Star Wars) or digital rejuvenations or aging of actors in sufficiently realistic quality.
A nice example for the "hidden visual effects" is "Roma", a film that looks so realistic that the normal viewer would hardly suspect a multitude of digital objects in it:
Bilder zur Newsmeldung:
;)
;)