Most restaurants offer either call ahead seating or reservations but did you know that there are distinct differences between the two?
I have not yet worked at a restaurant that takes reservations (with the exception of really big parties), but from my understand, there is a table waiting and ready for you at a certain time when you make a reservation. You always have to call ahead to make a reservation, otherwise you're usually out of luck.
Call Ahead Seating:
Different restaurants may do this differently, here is how I was taught. The restaurant I am currently at will only take names for CAS when the restaurant is on a wait. Bascially, no wait list, no way to do call ahead seating. We can't put your name on a list that doesn't exist! While people can get annoyed with this, for instance, if they call when they are on their way, and we are not a wait, we tell them so and do not take their names. However, by the time they reach the restaurant (and this happens frequently on busy nights), there are no tables left and the restaurant is now on a wait.
The second mistaken thought about call ahead seating is that if you call ahead, you will have a table waiting for you when you arrive, not true! That is reservatons. Call ahead seating simply puts your name on the wait list, just as if you had sent one person in your party ahead of the rest to put the name in to reduce the in-restaurant wait time. With larger parties, however, such as 8 or more, if an estimated arrival time is given, the hostesses (or hosts, where I am, there are only hostesses, so that is what I'll be using) will do their best to have something set up when you arrive, especially if more than one table is required. Nothing is ever garaunteed with call ahead seating either, unless you specify smoking or non-smoking (for the restaurants that still have smoking sections) or a table or a booth, usually those can be garaunteed.
I will have posts following this on how wait-lists work, etc. But right now, it's 2:30 in the morning, and I'm tired. Also, this post was merely to explain the difference between call ahead seating and reservations, because it would be a quick post. I hope it was insightful.