when there is a picture in a picture, we use the term, "inscribing" This is because, there is a picture, inside another picture.
If it's a picture of the same picture then it's known as the Droste effect. But a more generic for this is just a recursive picture.
what does these symbols mean on this picture
There are way, way too many with that feature to be able to answer here. The one piece of advice I will give you is that usually a TV with picture in picture will require an external input signal...
The English term 'get the picture' means get the meaning of something