You almost always meet Philharmonic in the names of large orchestras: the Vienna Philharmonic, the New York Philharmonic, the Taiwan Philharmonic. It means, in the name, ‘loving harmony’ or ‘loving music’. It can describe the orchestra (a philharmonic concert) or stand as a noun for the orchestra itself (‘the Philharmonic is playing tonight’). It sounds grand and a little old-fashioned; you would not use it for a school band or a pop group. In English it is often written with a capital P when it is part of a proper name. Some cities have both a ‘symphony’ and a ‘philharmonic’; the words are close in practice, and the difference is mostly in the organisation’s name, not in a different kind of music.