Similar to Internet telephony, Audio conferencing uses the internet to connect the audio calls between the users however conferencing includes making voice calls to multiple people (minimum of 3 people). The same applies to Video conferencing. A great app/social network to make audio and video conferences is Skype.
Once all users accept a friend request from each other you can now send messages, pictures, images and make audio/video calls to each other. To send an audio/video call to more then one person you have to make a group chat and then click on the call or video camera button. Even after you have made the call you are given the option to add more people as you can see above.
Video conferencing is very handy for businesses as it saves time from travelling from on city or country to another to have the meeting and therefore saves travel costs. However, a disadvantage to both video and audio conferencing is that if one or more users have low internet then it will be hard to see and hear the other participant as the video may buffer and the audio maybe received late or not clearly.