How is this used

This is a generac power cord. It has a 30 amp plug that goes into the bigger plug housing and then 20 fr of cable running to a 20 amp 250v plug with one blade sideways and one vertical with a ground on the bottom. I am not sure what this is used for. I have a generac 5500 w generator and just need to power two refrigerators and maybe a light or two.