CFX Pressure-Velocity Coupling
 

I'm using CFX and I noticed that I cannot change the Pressure-Velocity Coupling like in Fluent (SIMPLE-PISO-SIMPLEC). So reading the CFX-Help I found out that CFX, using a co-located grid, leads to a decoupled pressure field. My questions are: -what do they mean with co-located (non-staggered)? -why is the pressure field decoupled?