What is 201 File?

Legal Definition
A 201 file is a set of documents maintained by the US government for members of the United States armed forces. 201 files usually contain documents describing the member's military and civilian education history. A 201 file may also contain personal information such as home of record, and awards documents. Typically, a 201 file contains one or more of the following:

The 201 file is an important document for service members to maintain, as the documents it contains are important for access to benefits such as the VA Loan and the GI Bill.

Copies of the 201 file can also be requested from the National Archives by service members and their families.

201 file further contains demotions, forfeiture of pay as a de facto record of non-judicial disciplinary action (Article 15).

Court Martial and judicial action are recorded.

Weapons qualification is included in the 201 file.

The Central Intelligence Agency also uses the term "201 File" to refer to their own personnel records used for analogous purposes.
-- Wikipedia