Philosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness, and their relationship to the physical body, particularly the brain.
Questions about the philosophy of mind are, at their roots, about the nature of consciousness and how it relates to the world. They can branch from here into numerous problems:
What is consciousness "made of"? Are there fundamental building blocks, "qualia" of sensations from which every conscious moment is composed? Where do qualia come from? Are they physical stuff tied to our physical forms, or a different "kind of thing" entirely? Or is everything mental?
We perceive stuff, and from our perception we learn about stuff, but what is our perception itself made of? How reliable is it? Illusions, dreams, imagination, and implicit biases are all food for thought here.
Not necessarily separate from the above, but importantly scientific: what have we learnt from experiments about the mind? What do we understand about the brain and how it relates to our experiences of our own minds? From all this, can we extrapolate anything about artificial intelligence, e.g. whether or not robots can "feel"? Many ethical questions are seeded here.