Tapas are canapes Spanish style.
Each time you order an alcoholic drink in Granada at a Tapa's bar or a restaurant it is normal for them to give you a small plate of food called a tapa.
In other parts of Spain you have to order tapas.
In Granada they are normally free but that means that you can't normally choose exactly
which tapa to have.
Tapas can be just a few olives or can be much more elaborate.
Typical tapas could be:
Small pieces of manchego cheese drizzled with olive oil
Small squewer with bits of meat
Carne en Salsa - (Looks like dog food but much more tasty)
Many different sorts of fish or shellfish.
The average Spanish person would go out and have a few tapas with their friends during the evening.
It is normal to only stay in each place for 1 or 2 drinks.
The drinks are not particulary big.
Only a small glass of wine or a caña which is a small glass of beer.
After a few tapas most people will start to get a bit merry but it is not normal for anyone to be obviously drunk.
More serious drinking would be done after midnight at a "bar de copas" or a bar with loud music making it impossible to talk.
Here is a link to several good tapas bars in Granadahttp://granadamap.com/places/tapas_bars_in_granada.htm
There is a tapa guide by areas of Granada herehttp://granadainfo.com/tapichuela/indexen.htm
More info about tapas https://goo.gl/HLNDM6