The Spanish word feria originally designates a fair (agricultural, books, ...).
Its origins go back to 1879, 9 years after the town was first founded, the fair began when farmers gathered to sell and buy beautiful animals, usually drinking to celebrate the deals.
The other is a Theme Park/carnival style area where kids and grown ups can have fun on different rides such as roller coasters, bumper cars etc... At the Feria de La Línea all the casetas are public, so anyone can just walk into any one and enjoy the food, drinks, and dancing.
This is one of the main features that differentiates it from the Seville Fair as most of the "casetas" there are private and therefore only card holding members are allowed in.
In the casetas, throughout the day and night, people will usually be found drinking a traditional drink known as fino sherry, and in more recent years a new trend is to mix the fino with lemonade and ice cubes creating a cocktail commonly known as Rebujito.