What's interesting about the Italian usage of gestures is that it's para-linguistic (unlike a sign language), but it still conveys meaning alongside what's being said - sometimes, critical info.

Here's a bit of a dirty example. There's a gesture where you close both fists, but the index fingers are slightly lifted (while still curled), and you gently tap the inner side of the hands together a few times. If I were to use it alongside the sentence "Alice and Bob are in that room", the gesture alone conveys what they're doing (having sex).

They're also used for backchannel. It's outside the scope of the study, but basically: while one person is saying something, the other gestures their thoughts or metadiscursive info (like "go on").