When someone says food and drinks will be served they mean that guests will be provided with food and drinks. This is a respectful way to let everyone know what they can expect from the gathering they are attending. This can be quite helpful in the planning process when attending any sort of gathering. It lets you know that you will not have to plan to eat before or after the gathering because a meal will be served while you are there.
Now one can manage their time more appropriately and also be able to know what to expect without having to figure out the politest way to ask. Letting guests know this kind of information is a sign of a good host or hostess.