That means people can call you on that number and you can make outbound calls from it, typically by way of the provider's dialer app.
It might be a disposable or semipermanent number, but in the end, it really is the equivalent of a second line.
But calls can also be routed to one or more additional lines: office, home and so on.
You can use the Google Voice app to place outbound calls, send and receive text messages, toggle do-not-disturb mode, and play voicemail messages, which are also transcribed to text, a handy extra.
If you need it a little longer, the seven-day plan costs just $1.99 and includes 20 voice minutes and 60 text messages (including SMS).