This video more humbly should have been titled "Enlarging images, using bilinear or bicubic interpolation, explained".
This video does not touch the subject of resizing to smaller sizes (which is pretty difficult due to the ugly aliasing artefacts that can result) and it does not touch the many more sophisticated methods (like Sinc, Seam Carving, NNEDI3 etc.) - for more information, read on at https://en.wikipedia.org/wiki/Image_scaling
It looks like you're new here. If you want to get involved, click one of these buttons!