All platformers have multiple levels (also called courses or stages) which contain obstacles, enemies, items, and the like. Mario (or other characters) must pass through one level to get to the next and ultimately complete the game. In some cases, there are also levels that are hidden and need to be unlocked.
Levels appear in the Super Mario series. At the end of every level (except for castle levels) in Super Mario Bros., Super Mario Bros.: The Lost Levels, New Super Mario Bros., New Super Mario Bros. Wii, New Super Mario Bros. 2, and New Super Mario Bros. U is a Flagpole (or a Red Flagpole if it is a secret exit in the New Super Mario Bros. games) and Fortress. However, Super Mario 3D Land and Super Mario 3D World contain only a Flagpole at the end of each level. At the end of Super Mario Bros. 2 are Mask Gates. Most levels of Super Mario Bros. 3 end with Roulette Boxes, but Fortresses end with fighting Boom Boom and Airships pit Mario or Luigi against a Koopaling. Most levels of Super Mario World end with Giant Gates, but the castles end with fighting a Koopaling. Super Paper Mario has Star Blocks at the end of every sub-chapter after the chapter boss is defeated. In Super Mario 64, Super Mario Galaxy, and Super Mario Galaxy 2, levels end with the collection of a Power Star, while in Super Mario Sunshine, they end with the collection of a Shine Sprite. Each game has a unique ending for its levels, although the outcome is always progression to the next level.