Aesthetics, as you would have known the term in general sense, points at Art. It is the branch of philosophy which deals with questions of beauty and artistic taste.
Aesthetics raises some important questions about Art as mentioned below:
What is Art?
How does one evaluate Art?
What does Art do to us?
What is the purpose of Art?
These questions are not easy to answer. But the philosophers have tried. RG Collingwood, for instance, divided Art into two categories: Amusement Art (meant only for escape from real life) and Magic Art (changes how we interact with world)
Books on Aesthetics:
Introductory Lectures on Aesthetics By Georg Wilhelm Friedrich Hegel
On the Aesthetic Education of Man By Friedrich Schiller
Aesthetic Theory By Theodor W. Adorno
History of Beauty By Umberto Eco