By screen is generally meant a device of various shapes and sizes which can be used as protection, for example an insulating or protection screen, or a surface on which to visually represent still or moving images, such as for example a projection screen or a common TV.
The word shield, derivation of shielding (from the Germanic skirmjan, which means to protect), in modern language is understood more generically as an object interposed between two things, of various shapes and sizes, which performs the function of defense or protection.
There is a large variety of protective screens, e.g. radiation shields, acoustic screens, biological screens, etc. (for more details see protection screen).
Often the surface on which still or moving images are represented is also called "screen", there is a great variety, as an example of the most commonly used there are: