A musical ensemble is a group of several instruments used to perform music. There are several denominations according with their size and composition.
More instruments but still not too many are usually refered as a Chamber Orchestra.
A choir? is a group of voices.
A String Orchestra has only strings, i.e. violins, violas, violoncellos and basses.
A Symphonic Orchestra is a large body of several tens and often more that a hundred musicians, divided in groups of instruments: Violins I and II, Violas, Violoncellos, Basses, woodwinds, brass, percusion?, and some times more.
There is no difference between a Symphonic, a Philarmonic, a Symphophilarmonic, etc. orquestras. They are only names to distiguish them when there is more that one in a city.