What is 'Sonata form'?

Sonata form is the way in which a musical movement (usually the first) is structured. This can be broken down into 3 general sections, each with their own set of characteristics:Exposition- This section introduces us to the first subject, which is in the tonic key. Usually, there is then a transitional passage which brings us into the second subject, which tends to be in either the dominant or relative minor key.Development- This section takes material from the exposition section and transforms it through methods such as fragmentation and rhythmic displacement. It also goes through several modulations, which are changes in key. Recapitulation- The material of the first and second subjects of the exposition are now repeated in a shorter and slightly altered format, but are also now both in the tonic key.In addition to these 3 sections, there can also be an optional ‘introduction’ section, which begins the piece before the exposition enters. There can also be a ‘coda’ (or ‘codetta’ if it’s very short) section to end the piece and give it a sense of resolution.