Although Christmas starts on the 24th for most families, there are some Spanish pre-Christmas traditions. The most important is the Spanish Christmas Lottery, known as ‘el Gordo’ (the fat one) which is held on the 22nd December and is the biggest lottery worldwide. Apart from that, you usually watch ‘La Gran Familia’, a movie that is on TV every single year.
The night of the 24th is called Nochebuena. Religious people go to the church on the 24th to the ‘Misa del Gallo’ (something similar to midnight mass), but most of the families simply reunite in order to have a huge dinner (and eat way more than is recommended). Although this ‘feast’ may vary, it usually includes some appetizers (mainly Jamón Serrano), seafood, soups, lamb and a typical Christmas dessert (turrón and/or polvorones).