Which network is created by default when Docker is installed?

When Docker is installed, a network named "bridge" is created by default. This bridge network serves as a private internal network for the containers that are running on the host machine. It allows these containers to communicate with each other while isolating them from the host's network. The bridge network uses Network Address Translation (NAT) to route communication between containers and the outside world, ensuring that containers can interact without exposing the entire host network.

This default configuration offers a simple solution for container networking, making it easy for users to quickly deploy applications in a Docker environment without requiring additional setup. Containers connected to this bridge network can communicate with each other directly through their automatically assigned IP addresses, while still having the flexibility to access the host network if necessary.

The other options, such as "host" and "overlay," refer to different networking modes. The host network mode would allow a container to share the host's networking namespace, while the overlay network is used for multi-host container communications in a Docker Swarm environment. However, these are not the default network types created when Docker is installed. Thus, the bridge is the correct answer for the default network created.