Echoes while using voice and video chat are caused by feedback between the speakers and microphone. If you hear an echo while talking, the problem is likely on your contact's end. We recommend reducing the microphone and speaker volume or changing the speaker orientation on both sides to ensure that the speakers are not too close to the microphone. It's also possible for one side to mute while the other side is talking to reduce this feedback. Either party can mute by clicking the blue microphone icon in the chat window. Clicking it a second time (while it is covered in an X) will unmute.
The best way to avoid echo is to use headphones on both ends of the call.