This video provides a comprehensive understanding of posting keys and field status variants in SAP S/4HANA Financial Accounting (FI). Here are the key points:

1. Posting Keys: The video explains that posting keys are control indicators used in financial document posting. For example, when posting any financial document, debiting any customer, vendor, or general ledger account, or creating some customer vendors and ledger account, posting keys are used. Posting keys are defined in the system, and while customized posting keys can be created, it is not recommended to do so. SAP recommends using system-defined posting keys.
2. Field Status Variants: Field status variants are used to define the fields available during document posting. For example, if you are posting primary costs and need to make the cost center mandatory, you would use a field status variant. Field status variants can make fields mandatory, optional, or suppressed during document posting.
3. Defining Field Status Variants: The video demonstrates how to define field status variants. It shows how to copy an existing field status variant defined by the system and assign it to a new field status variant.
4. Assigning Field Status Variants: After defining a field status variant, it needs to be assigned to the company code. The video shows how to assign a field status variant to a company code.
5. Assigning Field Status Groups to General Ledger Accounts: The video shows how to assign field status groups to general ledger accounts. For example, if you want to make the cost center mandatory when posting to a salary account, you would assign the appropriate field status group to the salary general ledger account.