Bach wrote this Partita about 300 years ago, no one knows exactly when. The work has that mysterious BWV 1004. Let's talk about that. In 1850, the Bach Gesellschaft started publishing all of Bach's works that were known. They were just bundled up and an edition was put out each year. Sincere there were well over 1000 known this obviously went on for many years. In 1950, a musicologist named Schmieder re-cast the entire set in a set of volumes that would break your back called the Bach Werke Verzeichnis or BWV. As this set of editions included everything that was unearthed or missed by the Bach Gesellschaft publications, it was adopted as the holy grail so to speak and since Bach wrote a lot of the same kind of music, the BWV numbers help keep one sonata from being confused from another. So the work below is Partia BWV 1004. In chronology this isn't the 1004 work he wrote but merely is the 1004th in the list to be published in the BWV volumes. Sometimes you'll hear these pieces given a "Schmieder Listing #" after the guy musicologist so don't be confused.
Anyway BWV 1004 (see how much you have learned) is incredibly difficult. It may look just like a pile of notes but it can be played so badly as to make you cry and so well that it produces the same effect. Johannes Brahams, one of the composers who subscribed to the Bach Gesellschaft publication of these works (a little known fact but true) when he encountered a movement from this Partita, wrote:
"On one stave, for a small instrument, the man writes a whole world of the deepest thoughts and most powerful feelings. If I imagined that I could have created, even conceived the piece, I am quite certain that the excess of excitement and earth-shattering experience would have driven me out of my mind".