ARPANET was the world's first operational packet switching network and predecessor to the Internet, developed by ARPA during the Cold War. A soft bounce occurs when an email reaches the recipient's server but bounces before delivery, while a hard bounce means the message is permanently undeliverable. Computer spam refers to annoying messages or ads that flood computers when accessing the internet or using email. An intranet is a private network, protected by passwords and only accessible to authorized users like employees, whereas the Internet is a public space.