In a nutshell, talking heads are scenes or paragraphs where characters are talking back and forth without any description, action, beats, or inner monologue. This can make for lifeless reading not to mention it's very confusing.
Character action and beats- This is one of my favorite ways to break up dialog. Instead of using a tag (he said), use a beat (he clamped his hand to his forehead). This conveys something about the character, as well as letting the scene play out like a movie in the reader’s mind. Characters can pace the room, stare out the window, run their fingers through their hair, clasp and unclasp their hands - the sky’s the limit. Of course, keep in mind who your character is and whether or not they would perform that particular action.
Description– This pretty much goes hand in hand with character action. Having your main character sit down on a leather desk chair instead of just a chair can go a long way in describing the setting. This is especially true in historical novels where readers may not be familiar with objects used in the era. Characters can wash a sink full of dirty dishes, flip through the New York Times, or sip tea from Dresden china cups. You name it. Using description in this manner can work to your advantage and eliminate what would usually be boring dialogue.
Although some dialog is best presented in a ping pong style (such as some scenes in mysteries or thrillers) this can wear the reader out. Readers want novels that drop them into the story and into the character’s mind. The more an author immerses them in the thoughts of a character and in the mood of the scene, the more the reading experience will deepen. Of course, there can be overkill, but as I tend to err on the “talking head” side, rather than the “overkill” side, I always need reminding.