Assuming a situation, where we need to create two schemas with the same name in the same database. Is it possible???? No, it is not possible......

When it's required? 

When we want to install two application like PeopleSoft/EBS in the same database because some application which has a specific schema name -SYSADMIN in PeopleSoft or AP/AR/GL ect..ect required for EBS Case. 

What was the option in prior 12c?

We could create two different databases but with two different databases comes two different sets of overhead - two instances which consume memory CPU The more databases you have, the more the CPU and memory usage - all because you want to create multiple schemas in the same name. 

In 12c we can achieve above goal.

In 12c, Oracle introduces multi-tenancy option. Instead of creating a physical database for each SYSADM schema you want to create, you can a virtual database for each schema. 

Each virtual database behaves like an independent database; but runs on the top of a real, physical database which may be hidden from the end users. 

These virtual databases are called Containers. The physical database that houses these containers, is known as a Container Database (CDB). You can pull out (or "unplug") a container from one CDB and place it (or, "plug" it) into another CDB. This is why a container is also known as a Pluggable Database (PDB).