Tapas as we know them today have only been around for about 50 years... and the way of serving and charging for them varies considerably.
The traditional version of how they got their name springs from the probable myth that King Ferdinand was invited to have a drink at a bar in Cadiz, but, as would have been the case everywhere, the place was buzzing with flies. The conscientious barmen, to protect the sovereign's drink, placed a small piece of cured ham on top of the glass - and voilà - the tapa got its name.
The rule is that tapas come free, and if you get one with the first drink you never know what happens with the second. Usually it comes without, and it is not polite to ask for a repeat. You will get it, but with a sour face, as even if you offer to pay for it, you will not be able to.
'Tapas' are different everywhere. In the Basque country they are known as pintxos, spiked through with a toothpick. The bill is arrived at by counting the number of 'palillos' on the plate.
Granada is a tapa-lover's paradise, and the generosity of the portions is legendary. It is not unusual to be served a large slice of tortilla or a Russian salad with every drink at no cost.
The economics are baffling, but of course your free tapas will never feature jamón or queso curado.
Although everyone has their own favourite tapas bar, Malaga province is not renowned for the quality or the generosity of its tapas, and we need to go to Seville or Jaén to appreciate that.