Tapas are essentially snacks. In many regions of Spain they are often included in the price of drinks (beer, wine, not soft drinks or spirits) served in bars. In this case, they can amount to as little as a few olives, a piece of cheese, or something more substantial like a pork stew. Bigger portions that are ordered to make up part of a meal are called raciones. The portions are usually shared by diners, and a meal made up of raciones resembles a Middle Eastern mezze or a shared Chinese meal.
The Spanish eat dinner late, and often go "bar hopping" and eating tapas in the time between finishing work and having a full meal. Some believe that it is this constant change of bars that helps keep the participants of a "tapas crawl" awake.
Tapa means "cover" in Spanish. While there exist various explanations for the etymology of "tapa", a commonly cited explanation is that an item, be it bread or a flat card, etc., which would often be placed on top of a drink to protect it from fruit flies; at some point it became a habit to top this "cover" with a snack. Equally popular is the theory that it "covered" the appetite between finishing work and eating the evening meal, usually sometime after 10pm. In the Philippines, this “cover” evolved to become a thin strip of beef which is nowadays eaten, along with rice, as a full meal, usually for breakfast.
In the northern Spanish city of León, and in parts of southern Spain (Andalucía), when you go to a bar and order a drink, you get a tapa for free. This happens mostly in the province of Jaén, Granada and Córdoba but it is not very common in the rest of Andalusia, where you have to pay for both the drink and the tapa. They are also called pinchos/pintxos, because many of them have a pincho, or toothpick through them. This is used to keep whatever the snack is made of from falling off the bread it has been attached to. Another name for them is banderillas (diminutive of bandera "flag"), in part because some of them resemble the colorful skewers used in bullfighting.
It is very common for a bar or a small local restaurant to have 6-8 different kinds of tapas in warming trays with glass partitions covering the food. They are often very strongly flavored with garlic, chillis or paprika, and sometimes swimming in olive oil. Often one or more of the choices is seafood or mariscos, often including anchovies, sardines or mackerel in olive oil or squid or others in a tomato based sauce, sometimes with the addition of red or green peppers or other seasoning. It is rare to see a tapas selection not include one or more types of olives, such as manzanilla or arbequina olives. One or more types of bread are usually available to eat with any of the sauce-based tapas.
Upscale tapas restaurants are common in the United States, where a series of tapas are typically served as a main course. The UK has a tapas chain, La Tasca, which recently opened a branch in North America.

Common tapas include:

• Chorizo al vino
    Chorizo sausage slowly cooked in wine.
• Gambas
    Prawns sauteed in salsa negra or garlic.
• Rajo
    Pork meat seasoned with garlic and parsley.
• Zorza
    Rajo with added paprika.
• Queso con anchoas
    Castilla cured cheese with anchovies on top.
• Ensaladilla
    Mixed boiled vegetables with tuna, olives and mayonnaise.
• Tortilla
    De patata (potatoes) or paisana (mixed vegetables and chorizo), a type of omelette, similar to fritatta.
• Allioli
    Very strong garlic paste, sometimes simply garlic mayonnaise. Served on bread.