To refrigerate something is to preserve it by keeping it cool. A gallon of milk might last a week if you refrigerate it, but it will be spoiled after a day or so if you leave it on the kitchen counter.
At home, you refrigerate things all the time by keeping them in your refrigerator. If there's no refrigerator available, people can refrigerate things by storing them in coolers or outside in the cold months of the year. A recipe for cookies might instruct you to refrigerate them for an hour before baking them — all you have to do is put the baking sheet in the fridge. Refrigerate shares a Latin root with frigid.