What’s the difference between the terms “symphony” and “orchestra”?

A symphony is a large-scale musical composition, usually with three or four movements. An orchestra is a group of musicians with a variety of instruments, which usually includes the violin family.

A symphony orchestra (often just called “a symphony” for short) is an orchestra that has both the number of players and types of instruments required to play a symphony.

And philharmonic just means “music-loving” and is often used to differentiate between two orchestras in the same city (e.g. the Vienna Symphony Orchestra and the Vienna Philharmonic Orchestra).

This article also has great information about this topic.