Why buffering is used in SAP DDIC table? Where is it located and its usage?

Buffering is available under Technical Settings in SE11.
Buffering has 3 options.
SAP buffering can be permitted for a database table as follows:
Buffering not allowed
SAP buffering is not performed for the table. Open SQL always accesses the current data of the data table directly. This setting also dictates that SAP buffering should also not be activated for this table in any other systems due to the way it is used.
Buffering allowed, but switched off
SAP buffering is not performed for the table when delivered. This setting dictates, however, that buffering is possible in principle and can be activated in other systems depending on how the table is used.
Buffering switched on
SAP buffering is performed for the table. If possible, Open SQL statements access the SAP buffer in the shared memory instead of accessing the table directly.