Honestly, I am quite blur when it comes to VoIP even though my husband own an internet cafe and offers this service to his customers. So, to brush up my knowledge about VoIP, I go to Vonage website to read their news, reviews and forum.
In the Vonage Forum there's a link about Vonage Information. Under Vonage FAQ, everything that I need to know about Vonage is there. Like What is Vonage, What is VoIP, How to get Started etc.
For those who are planning to switch to Vonage, I would suggest you read about the pros and cons in the Vonage Reviews which is written by the current user of Vonage. If you really take time reading the reviews and forum, you might get good tips from other user like what I discover...free second month promotion but must sign up thru the Vonage rebate link.
If you can't find the answer to your question, you can always put it up in their forum. I am sure we will get the answers from Vonage customer service or other friendly Vonage user.