What does a "twin" versus a "double" room mean as far as bed sizes? Thank you.
Both rooms are for 2 people. Generally the twin is 2 single beds and the double is a larger bed for two people. In some cases the "double" bed is 2 twins pushed together and covered with a single coverlet.
You could even have a quad room (for 4 people) with four twin-sized beds...it varies by lodging.
Lola is right. This is a confusing subject. Strange as it seems, in some cases, but not always, a 'twin' room is actually larger than a 'double' room (due to the space between the beds.) You have to clarify all this with the particular place you are considering. There will be an upcharge, but if you are interested, it is also possible to find queen or even king beds in Spain.