In the example video shown you can use the Chroma Key effect and select the color of the shape of Spain in the Chroma key effect. This will make that part transparent. Then anyone on a track underneath will show through the transparent part(s).
That is specifically for that example. Generally speaking, to get something to “show through” a part of a video you need some parts of the upper event to become transparent. There are many ways to create transparency. In Vegas, Chroma Key, Mask generator, Cookie Cutter, Secondary Color corrector and actual event masking can accomplish this. Each have their uses depending on the source material you are trying to create transparency from.