The twelfth lunar month is called 腊月 ("la" month) and this festival is celebrated on the eighth 八(ba), hence it is called Laba Festival.
Originally it started as a day for worshiping gods and ancestors, after Buddhism was introduced to China, it also became associated with the Buddha. Some of the most well-known foods associated with this festival are Laba Congee (made with healthy grains, beans and dried fruit) and green garlic. In Northern China, cloves of garlic are pickled in vinegar which eventually turns them bright green.