What does the cable specification means?

Hey,
What does these cable specifications mean?

750 KVA Transformer to main panel
5RX3.5C X 300 Sq.mm
Generator to main panel
2RX3.5C X 300 Sq.mm
Main panel to cooling tower panel
2RX3.5C X 300 Sq.mm
Main panel to boiler area panel
2RX3.5C X 240 Sq.mm
Main panel to APFC Panel
2RX3.5C X 240 Sq.mm
Boiler panel to Boiler MCC
1RX3.5CX70 Sq.mm
Main panel to utility panel
1RX3.5C X 70 Sq.mm
Boiler panel to Fuel and Ash handling MCC
1RX3.5CX50 Sq.mm
Utility panel - Dry goods panel 35KW
1RX3.5CX50 Sq.mm
Cooling panel to plant cooling tower Pumps 60HP( 3 Nos)
1RX3.5CX50 Sq.mm