What is a deepfake in artificial intelligence $($Al$)?$

a hypothetical type of an Al model that is capable of thinking and reasoning like a human

a technique used to manipulate media $($videos or images$)$ to appear realistic, but are actually fabricated

a technique used in Al to generate realistic and accurate human$-$like chatbot responses

a type of neural network that uses deep learning algorithms for processing data

I don't know this yet.