The ‘pause’ container is a container which holds the network namespace
for the pod. Kubernetes creates pause containers to acquire the respective pod’s IP address and set up the network namespace for all other containers that join that pod.
You can access below links for details.
https://groups.google.com/forum/#!topic/kubernetes-users/jVjv0QK4b_o
https://www.ianlewis.org/en/almighty-pause-container