This likely refers to a collection of Bach's instrumental suites, such as the English Suites, French Suites, or Partitas, which are foundational to the keyboard repertoire. They are distinctive for their intricate dance movements and masterful contrapuntal writing.
Mastering the intricate contrapuntal lines and achieving a clear, articulated style are crucial for performing Bach's suites.
Bach Suite is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
Bach Suite is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.