CAS (Column Address Strobe) before RAS (Row Address Strobe) or vice versa determines whether the column or the row gets referenced first, when the computer is addressing a location in memory.
Static column DRAMs have faster memory access (if the architecture supports it). They let the CPU specify only the row address of multiple memory locations in the same column. The first address is addressed by specifying both the row and the
column. After this, the column location can be omitted because it is retained. This is why it is called static column DRAM.