"Tapas" are essentially snacks. In many regions of
Spain they are often included in the price of drinks (beer, wine, not spirits) served in bars. In this case, they amount to as little as a few olives, a piece of cheese, etc. Bigger portions that are ordered to make up a meal are also called "tapas". It is customary to share them.
"Tapa" means "cover" in Spanish. The name comes from the card that used to be put on top a drink to protect it from flies; at some moment it became a habit to top this "cover" with a snack.