Hello Karthik
VSF and LSF are requirement type of MTS Planning Strategy 40 and 10 respectively.These are differed in consumption of Planned Independent Requirement.
VSF - PIR will be reduced when we receive Sale order.
LSF - PIR will be reduced when PGI against Sale order is done.
These all depends upon the consumption periods maintained in MRP3 view.
Below link from SAP Help
Table of Planning Strategy Assignments - Demand Management (PP-MP-DEM) - SAP Library
Regards,
Velmurugan S