The Makita DJN161Z is an 18V nibbler with single-speed operation. It has a maximum cutting capacity of 1.6mm in mild steel. This body-only version does not include a battery, charger or case, so these will need to be obtained separately before use.
The Makita JN3201J is a 110V nibbler with a 710W motor and single-speed operation. It is used for cutting sheet metal, with a maximum cut capacity in mild steel of 3.2mm. You will need this type of tool when you want a powered option for controlled metal cutting work.