According to GoSpain.About, here's what the little guys are all about:
Tapas is not a particular type of food. Anything can be tapas - paella, croquettes, ham and cheese on toast, truly anything. As long as it is small and served with your drink (either free or at a surcharge), it is tapas. It doesn't even have to be Spanish - in Granada there are a number of Morrocan bars that offer cous cous, falafel and kebabs as tapas.
Tapas is not a starter. If you start eating tapas, you finish eating tapas, and you don't stop until you're full.
Tapas is not a collection of small dishes brought out on a platter and eaten as a main course. The Spanish have a word for this - 'tabla'.
The Meaning of the Word Tapas
A 'tapa' is a 'lid' or 'cover'. In the early days of tapas, a slice of cheese or ham was given with your drink and placed over your drink. There is some debate over why exactly this was done.
Now THERE'S a debate worth having!