The concerto is unique for other reasons also, as will be told in the analysis below. It was composed for strings, two oboes, two horns and soloist, but Mozart's skill in using the forces at hand makes it sound much larger than that. It is in the customary three movements:
I - Allegro
Mozart begins the concerto with a flourish for the orchestra, which is immediately answered by the solo piano, a novel idea at the time for the soloist usually didn't enter until the orchestra played an exposition of the themes. This sets the tone as the piano has other surprising entrances at different times as well as its traditional statements of the themes of the movement.
II - Andantino
This movement is written in C minor, the relative minor of the home key of E flat major. Mozart wrote only five concertos that had middle movements in a minor key. Mozart has the piano sing a sad, melancholy song while the orchestra accompanies. It is like a scene from a tragic opera, one of Mozart's most heart-felt slow movements.
III - Rondo : Presto
The piano plays an extended solo at a brisk tempo, the orchestra replies. Mozart keeps up the pace, with piano and orchestra trading comments and taking turns accompanying and soloing. After a few episodes and return of the rondo theme, the piano plays a short cadenza that leads to a gentle minuet. The minuet is played and developed as a separate section until the piano plays another short cadenza that leads back to the theme of the rondo. The music runs helter-skelter to the conclusion.
A word about the performance in the video below. This was played on a copy of a piano like Mozart would have played on. To distinguish this kind of piano from the modern instrument it is sometimes referred to as a fortepiano. The piano of Mozart's time was markedly different from the modern instrument. The keyboard was smaller, five octaves compared to seven and a third, the frame was wood compared to iron, lighter hammers and action, different tone qualities in different parts of the keyboard, considerably less volume than a modern instrument. These qualities will be evident in the recording. It gives the listener an idea of why concertos were written as they were. With an orchestra that could drown out the soloist the problem of balance between the two is crucial. I much prefer the sound and tone of a modern instrument, but recordings made with period instruments can stretch the ear of the listener. And we all need to keep our ears 'stretched'. You never know when you might hear something different and interesting.