A symphony was split into 3 movements as within a symphony rules were made and had to be stuck to which is what gives us this rigid structure. It is a large orchestral piece.
Movement 1: was written in a sonata allegro form.
Movement 2: was slower and played una different key with a stronger melody line.
Movement 3: was much livelier played in a major key, more light hearted and written in rondo form. Was stylistically ligher than other movements to keep listeners interest.
Concerto: a piece of music for a solo instrument and orchestra. Diatonic music - music that only uses notes of the key (no clashy sounds).
Even phrases - regular chunks of music, as if separated by commas.