In general, a suffix like “L01” would indicate a logical file (LF) built over the physical file (PF) that is named the same as first part of the LF name. “L01” would be the first LF over that PF.
A LF is similar to a SQL VIEW or INDEX. A PF is similar to a SQL TABLE.
Some LFs might be defined in a way that returns only “active records”. Or the definition might be intended only to provide a particular index sequence for sorting or for randomly reading records by key values.
Use DSPFD to see the details of the ILIL01 file description. Use DSPFFD ILIL01to see details of the file field descriptions.