Some questions about the microservice.

Hello,
According to the Red Hat and Google:
Quote:

Linux containers give your microservice-based apps an ideal application deployment unit and self-contained execution environment. With microservices in containers, it's easier to take advantage of hardware and easily orchestrate services, including storage, networking, and security.

And:
Quote:

Microservice architecture - a variant of the service-oriented architecture structural style - arranges an application as a collection of loosely coupled services. In a microservices architecture, services are fine-grained and the protocols are lightweight.

My questions are:

1- Why some administrators prefer microservices?

2- Microservices are applications that running in a container? For example, an Apache Web Server that running inside a container like Docker.

3- Is Unikernel something like the microservice?

Thank you.