Hi salma_z, the parking on the top/right is for regular taxis to park like open to all, a taxi can drop you off inside it, or you can take a taxis etc. The 2nd parking lot on the left/south is for authorized Taxi companies (not public taxis), these Taxi companies like "Taxi al-Mumayz", "Taxi al-Musafer", "Taxi Baghdad" and others are authorized and regulated by the Airport/Government like have a fixed fee unlike regular taxis and they can also park at the terminal gate, have internet, GPS monitoring, etc..    
Regards.