A large and consisting of a lot of movement works for an orchestra is called a symphony. A symphony is usually long, but it actually does not have to be that long according to the definition. The European-based music usually has from three to four movements (movement means a piece of music which can stand on its own but is created to fit in with the stream of ideas that build up the symphony). The first movement is usually a mini sonata with a lively tempo. The second movement contrasts with the first one with a slow tempo and the third movement will be a lively or an elegant dance-like work depending on the contrasting meter (usually 3/4 or 6/8). The last movement is often a loud mini sonata filled with joy to send the audience home with a smile on their face.
Symphony uses instruments from all four sections (strings, brass, percussion and winds) and seeks for all spectrums of rhythm, harmony, dynamics, timbre and melody. The word symphony means “sounding together”, which is the reason the symphony requires the combination work from all four sections. That was the basic definition of a symphony; however as mentioned before, there is no perfect rule so a number of exceptions may arise.
How big is a standard symphony orchestra and how long does it usually last? Because there is no rule about this, the scale and length totally depend on the symphony itself.
Symphonies never consist of choir or singers; except, you know, when they do. In 1824, Beethoven created this exception by combined four soloists and a choir in the final movement of his Ninth Symphony. After Beethoven’s Ninth Symphony there are few composers who have also used the choirs in their symphony to add the text element; however it does not become any more common. Later on the size of symphonies grows bigger and bigger, until it becomes an epic, dramatic interpretation. Composers start to write less of them but the symphony becomes longer and utilizes more elements as well as forces.
Of course, this is just a brief description to point out similarities and differences between these definitions. You can find a great diversity within each definition, especially in the number of movements. The most decisive distinction is that symphonies and concertos include an orchestra, while partitas and sonatas do not. There are sure to be exceptions, for example the Bach’s Italian concerto was created for a solo harpsichord. Here Bach used the term concerto to emphasize on the structure and the mood, rather than an instrumental choice.
Speaking of mood and tone, concertos have the tendency to be brilliantly entertaining pieces. Sonatas and symphonies are generally more complicated and intellectually profound. Partitas have all their movements set in the same key so they can be considered to be an exploration of all the possibilities given by this tonality. But still, those are all just a brief guideline; an even deeper insight on those term can always be found in many technical books.