Skype app. Download and install it on your device. Then all you have to do is sign in and start text, audio or video conversations with your contacts.
Starting with the iPod 4 you can use the front camera you can not only see the person you are video chatting with but also broadcast to you friend so they can see you as well. True two way video conversations were made possible on iPods starting with iOS 4.0 and the iPod touch 4. Evidently Skype video chat also works with later versions. Devices that do not have a front camera will not be able to send videos but they will still be able to view videos that are sent to them.
When this Skype mobile feature first came out it was only available to Apple devices but now it's available on other smartphones that don't run Apple's iOS.