The number of images is different

Currently, when I build image from Dockerfile which using FROM node:8 instruction, there are 2 images using docker images. One is for node image and the other is for own image. I assume it’s called sample image.

Then, I would use docker push for sample image and it still is working when pulling that image from docker hub as creating container on that image without node image.

The question is why is the container working without node image?
Anyone help me with this. Thanks in advance.

There is only one image if pull that image from docker hub but two images if I use docker build including node and sample images.