I was wondering how is it possible to create something like the attached picture. It is a screenshot from Google Earth: as you can see, by clicking on a dot on the map, a tab pops up that contains some information. For instance, some links are available, as well as a short description, and an embedded Youtube video. I am wondering if it is something that can be done within Google Maps/Earth, or if a third party tool is needed.
You need to create a KML file:
Don't expect to be able to create the example above in five minutes - start with the basics, create a simple pins, then go to the more advanced stuff with popups and HTML and whatever.
There may be a way in Google Earth that you can view the KML source for your example which you can use for learning purposes.