A slider is a small sandwich, typically around 3 in (7.6 cm) across, served in a bun. The term primarily refers to small hamburgers, but can also cover any small sandwich served on a slider roll. The term, when used in reference to a small hamburger, originated with the fast food

Fast food

Fast food is the term given to food that can be prepared and served very quickly. While any meal with low preparation time can be considered to be fast food, typically the term refers to food sold in a restaurant or store with preheated or precooked ingredients, and served to the customer in a...

 chain White Castle

White Castle (restaurant)

White Castle is an American regional fast food hamburger restaurant chain in the Midwestern United States and in the New York metropolitan area, and the first of its kind in the US. It is known for its small, square hamburgers. Sometimes referred to as "sliders", the burgers were priced at five...

, which trademarked the spelling variant "Slyder" and used it between 1993 and 2009.
Sliders can be served as an hors d'œuvre/appetizer, amuse bouche

Amuse bouche

An amuse-bouche or amuse-gueule is a single, bite-sized hors d’œuvre. Amuse-bouches are different from appetizers in that they are not ordered from a menu by patrons, but, when served, are done so according to the chef's selection alone...

, or entrée

Entrée

An entrée is a dish served before the main course, or between two principal courses of a meal.The disappearance in the early 20th century of a large communal main course such as a roast as a standard part of the meal in the English-speaking world has led to the term being used to describe the main...

.