Your homework consists of all devices you use for going online. Each of them is assigned a private IP address by your ISP. The goal of this mark is to let all the machines 'see' each other.
When you need to connect to the Internet, you need another IP-address that is defined as public. That address becomes your identifier, and private addresses will become invisible to external systems. All devices with unique private addresses will use that public IP address, one for them all.