Dan,

I should have been more specific there. Webopedia states that call quality is not as good as normal telephones. That statement is probably quite old now, and in my opinion VoIP continually meets and in most cases betters the quality of normal PSTN telephone calls.

Take your example of talking to someone in Africa.
Your call quality/delay is dependant on certain factors.

In no particular order:
Your hardware/software phone
Your internet connection speed
Your VoIP provider

Now, if everything is in order there is no reason why you can have crystal clear calls to Africa with no delay. Best of all… Its usually a LOT cheaper than normal telephone calls.

Is this the same technology as video conferencing?

That depends. Video conferencing can take place a number of ways, if your usually conferencing over the internet.. then yes its similar. At the end of the day, its just transferring data over the internet instead of the standard phone network.