Correct name of transparent instructional overlays / coach marks for announcing new features or first time use?

I find always more often when using a mobile app for the first time, these kind of instructional overlays or coach marks which illustrate to the user the basic gestures and menus of an application.

Below is an example on Android:

and here an HTML example in tumblr:

I cannot however find a consistent name for the above which would be an interesting tool also for Desktop apps even though I never see them used for instance in C# or Java applications but only mostly in mobile apps and web apps.

I also wonder if other platforms may use specific nomenclature of the functionality, in that case what is the naming for the same functionality on the different platforms?