Final answer:
A reservation usually guarantees a specific table at a predetermined time in a restaurant, similar to the etiquette of placing a napkin on your lap promptly when seated. A call-ahead is a courtesy that doesn't guarantee a table and is similar to the flexible nature of how long to wait on hold on a telephone call.
Step-by-step explanation:
The difference between a reservation and a call-ahead is that a reservation typically involves setting aside a specific table or setting for a customer at a restaurant for a particular time, and it often guarantees that the customer will have a table when they arrive.
This is similar to behavior etiquette where one would normally place the napkin on their lap as soon as they sit at the dining table in a restaurant, showing readiness for the meal and a thought-out plan similar to a reservation. On the other hand, calling ahead is usually more of a courtesy to let the restaurant know you're coming, but it doesn't always guarantee a table, especially during busy times. This is akin to how long one waits on hold on a telephone call; it's more informal and dependent on the situation.