The story is told that whenever the Cambridge Professor G.E. Moore was asked to define Philosophy, he would answer by gesturing towards his bookshelves: "It is what all these are about". It is just as difficult to give a definition of Philosophy as it is to explain the nature of Mathematics to someone who has no training in counting and calculation. One way of starting is to follow Moore's example. Philosophy is the main subject of most of the writings of philosophers from Plato and Aristotle to Aquinas, from Descartes to Kant, from Hegel and Marx to Wittgenstein and Sartre. You will learn what philosophy is by studying its history.
Another way (of starting) is to mention some of the problems philosophers are typically concerned with. Am I free to choose and act or are my actions predetermined? In what ways, if at all, am I different from my computer? Am I the same person that I was yesterday? Am I entitled to say that I know anything? Are there standards of morality that apply to everybody and in all circumstances? Should I ever break the law? Can I prove that God exists? What is truth? Can there be empty space or eventless time? Are aesthetic judgements objective or subjective?
You should not expect lecturers to give you easy, ready-made solutions to such problems. But they will encourage you to think about them systematically, to discuss them rigorously, to argue about them. You might come to realise as you proceed that some problems are much more complex than you might have thought.
Philosophy pursued as an academic discipline is a tough but extremely rewarding affair. A good dose of curiosity and a passionate concern for Truth is what you must have in order to start.