what is Tensorflow Quantum(TFQ)?
I'm one of the SWEs who worked on TensorFlow Quantum. I'll do my best to answer your three questions.


TensorFlow Quantum is a piece of software to incorporate the quantum computing primitives in Cirq into TensorFlow in a native and scalable fashion. It is primarily targeted at researchers.
Quantum computing is statistical in nature, TensorFlow is very useful for (among other things) statistical things like analyzing data and building models at very large scale. Having this ability to leverage the tools of TensorFlow alongside quantum computing workflows will hopefully lead to new research at scale that might not have otherwise been possible.
Hybrid quantum-classical machine learning is machine learning that involves both classical and quantum data. TensorFlow Quantum was designed with the goal of developing a better understanding of quantum data.


If my answers were too short for your liking, these sorts questions are also answered in greater detail over here and here.