Two reserve requirements the RBI imposes on banks: the Cash Reserve Ratio (CRR), a share of deposits kept as cash with the RBI, and the Statutory Liquidity Ratio (SLR), a share kept in safe liquid assets.
The CRR-versus-SLR distinction (cash with the RBI versus liquid assets with the bank) is a standard money-and-banking item.
CRR (cash, with the RBI, no interest) versus SLR (liquid assets including government securities, held by the bank); both differ from the concept repo rate (a price tool, not a reserve ratio).
CRR is cash kept with the RBI; SLR is liquid assets kept by the bank; raising either tightens lending.