The prompt is a series of characters used by any terminal interface to indicate that the terminal is ready to receive another command. Questions using this tag should be restricted to questions about the prompt, how to customize it, etc.
The command prompt (or just prompt for short) is a feature of any terminal system that lets a user know that the terminal is ready for its next command.
In most systems, the prompt can be customized or altered by editing various variables or configs (for example, Bash allows editing of PS1 to change the prompt).
By default, the Ubuntu prompt (through Bash) will look something like this:
ubuntu@ubuntu:~$
