Partita was originally the name for a single-instrumental piece of music (16th and 17th centuries), but Johann Kuhnau (Thomaskantor - 1722, followed by Bach) and later German composers (notably Johann Sebastian Bach) used it for collections of musical pieces, as a synonym for suite.
Johann Sebastian Bach wrote two sets of Partitas for different instruments. Those for solo keyboard the composer published as his Opus 1 (known as the Klavierübung I). One additional suite in B minor, the Overture in the French Style (often simply called French Overture) is sometimes also considered a Partita. Bach's Partitas are very rarely called the "German Suites", in analogy with the national naming of the English and French Suites. See Partitas for keyboard (825–830) and choral partitas for organ. The "Partita" in A minor for solo flute (BMV 1013) which takes the form of a suite of four dances, has been given the title "partita" by its modern editors; it is sometimes transposed for oboe.
Audio files 
Johann Kuhnau: a choral partita from 'Biblische Historien',
- http://www.jsbach.org/bwvs800.html contains the BWV listing including the Partitas (with their tonalities).
- Philipp Spitta, Johann Sebastian Bach: his work and influence on the music of Germany, 1685-1750, Volume 3 (Novello and company, limited, 1899) p. 156.