Afternoon tea is an old British tradition of having tea between 3 and 5 o'clock in the afternoon, accompanied by sweet or savory tidbits of food. There are three types of afternoon tea: cream tea, paired with scones, jam, and cream; light tea, paired with scones and sweets; and full tea, paired with savories, scones, sweets, and a dessert.
It is said that the tradition was invented by Anna Maria Stanhope, the Duchess of Bedford, in the 19th century. She suffered from a "sinking feeling" in the afternoon, so she started having a pot of tea and a light snack privately in her boudoir.
Today, afternoon tea is an occasional luxury or a birthday treat in a fancy hotel, and it is less associated with high society, since people in the United Kingdom tend to consume it multiple times a day, in numerous ways and flavors. Don't confuse afternoon tea with high tea because high tea is not as fancy and includes meat, fish, eggs, breads, and desserts.