You will probably notice that the flavours of a regular coffee and an iced one are quite different; an iced coffee tends to be less sweet.
Both drinks are coffee-based, and require ice. However, the biggest difference is likely to be the amount of milk added. An iced latte has a larger amount of chilled milk added to it, whereas a regular iced coffee can have no milk at all or just a small amount.
Because the coffee to milk ratio is different in these two drinks, an iced latte is likely to have less coffee content than an iced coffee. Therefore, an iced latte will be sweeter than an iced coffee. Another difference is the preparation. While an iced latte is not just a latte cooled down, an iced coffee can be made with espresso that is then chilled and poured over ice. A small amount of milk can then be added to taste.