Why do some foods taste better after they've been in the fridge for a day?

Certainly some of the types of foods whether cooked or even non-cooked improves the taste somewhat if kept refrigerated, due to the activity of certain enzymes that will bring about the decomposition partial to certain nutrients such as proteins its make the food more tasty  and it becomes easier to digest so it's best to keep the food refrigerated  meat or chicken short period before the process of cooking ...

See, as gelatin cools, it moves from a suspended colloidal state to a gel state, which if concentrated, can be quite strong. [...] And that is why our meat gets pretty hard when it cools down. Now, what’s really interesting, though, is that once gelatin has reached the gel state, it takes more heat to re-dissolve it than it did to render it from collagen in the first place. [...] Ahh, the meat is perfectly heated through, but it’s not falling apart. That’s because we let it cool down before reheating, and that is why stews, braises, fricassees, and banquettes are always better the second day.

During low-temperature storage in some foods, volatile compounds gather together to have better flavoring in some food. For marinated foods, condiments and spices reach every  of the food to have good taste. For liquid drinks, their ingredients have a better perception on taste buds if they are cool.

If it is cooked and seasoned and placed in the refrigerator for one day become imbued with spices and taste better, but if they cooked the taste change if placed in the refrigerator more than a day because they lose volatile components .