Labor day or otherwise known as May day for some celebrates the spring and working class of the country. It always occurs on May 1rst in Spain.
To celebrate many join in fun activities with family or just take the day off. Since it is a national holiday many of the hard workers of the country get to enjoy a day just for them.
The whole idea of having a labor day began with many countries and them over working their workforce and not giving them human rights. After plenty of riots it became a national holiday and a day to enjoy off for many workers across the world.