- ooVoo (pronounced = "ovu") is video call
- Skype (pronounced = "skaip") is similar to ooVoo but with less ability to provide multiple video calls
- Zello is PTT service (PTT = Push To Talk)
For Zello, you can create channel or you can join with your favorite community. All of these can be installed both on PC and mobile phone.
Rather different from both (ooVoo & Skype), for Zello, you have to push button (an image) to talk to someone, and release it to listen from other.
You can make a call from:
PC to PC
PC to Phone and vice versa
It requires android version 2.2 or above. I suggest you use flat rate for data plan (unlimited internet connection with fix payment for a month or a week, etc, depending on your communication provider).
More, latest from Facebook. You must install Facebook application and Facebook Messenger on your smartphone to make a free call.