What is philosophy? This is a notoriously difficult question. One of the easiest ways of answering it is to say that philosophy is what philosophers do, and then point to the writings of Plato, Aristotle, Descartes, Hume, Kant, Russell, Wittgenstein, Sartre, and other famous philosophers. However, this answer is unlikely to be of much use to you if you are just beginning the subject, as you probably won’t have read anything by these writers.
Philosophy is an activity: it is a way of thinking about certain sorts of question.
One important reason for studying philosophy is that it deals with fundamental questions about the meaning of our existence.
Another reason for studying philosophy is that it provides a good way of learning to think more clearly about a wide range of issues.
A further justification for the study of philosophy is that for many people it can be a very pleasurable activity. There is something to be said for this defence of philosophy. Its danger is that it could be taken to be reducing philosophical activity to the equivalent of solving crossword puzzles.
It is true that many of the problems with which professional philosophers deal do require quite a high level of abstract thought. However, the same is true of almost any intellectual pursuit: philosophy is no different in this respect from physics, literary criticism, computer programming, geology, mathematics, or history.