A knowledge base article about What's the difference between a YubiKey and a Simple Hardware Token? provided by the UC Berkeley IT Service Hub - Knowledge Portal
To use a YubiKey, once you’ve inserted it into a USB port, you can touch your YubiKey and it will automatically generate a code and complete the 2-Step. (See this page for images)
To use a simple hardware token, you will need to manually type in the code that it generates. (See this page for images). Simple hardware tokens are no longer available on campus but you can still use a simple hardware token as your 2-Step device if you have already registered one.