What are the difference between a power in VA and Watt?

Q. What are the difference between a power in VA and Watt?
A.
VA (Volt- Ampere) is input power of any electrical device, e.g. 120V*5A=600VA.
It means that device takes from electric line (120V) 5A.
Watt is output power of the same device (e.g. UPS, Transformer, Power Supply), 120V*3A=360Watt.
Different is 360/600=60%. 60% is Power Factor or Power Efficiency of the electrical device. For e.g. Transformer has input 1000VA and 800Watt output. Power Factor is 80%.
20% lost inside transformer on a heat.