What does network isolation mean?

Network isolation means that containers in Docker do not see each other and cannot connect to each other unless they are in the same network. Each network is like a separate "pocket" or room: what is inside is visible, what is outside is not.

What this gives you:

1. Security Containers do not get access to other containers' services unless explicitly joined into the same network.

2. Manageability You can group microservices: some containers talk to each other, others are isolated.

3. Predictability No "random" connections, only the ones that are specified.

Summary: network isolation is a mechanism that divides containers into separate network areas, so they cannot interact with each other without explicit permission.