Philosophy literally means "philo" (love) "sophy" (wisdom), i.e. "love wisdom". The ancient Greeks used this word to indicate those who has or love wisdoms.
My previous answer just mention what is the literal meaning for the word "philosophy". Regarding the question "what is philosophy"? The answer will be simple: now philosophy is a subject, a discipline. Basically it includes some areas: metaphysics, epistemology, ethics, value fields, and so on.