Spain has a mixture of traditional, religious, national & regional holidays. You will find that all banks, the majority of shops and most public buildings such as museums will be closed on these public holidays. However, bars and restaurants in the major cities and tourist areas will tend to remain open.
If a public holiday falls on a Sunday it may be celebrated on a weekday (depending on the region). When a public holiday falls on a Thursday or Tuesday, many people will take a long weekend ("hacer puente" in spanish - literally "make the bridge") by taking time off .