Of course it is well known that Anna the Duchess of Bedford is given credit for introducing Afternoon Teas to high society. An event of light eating with tea is also called Low Tea because it was usually taken in a sitting room or withdrawing room where low tables (like coffee tables) were placed near sofas and chairs.
During the second half of the Victorian period known as the Industrial Revolution, working families would return home exhausted as they usually worked the day without a break. The table would be set with any number of meats, bread, butter, pickles, cheese and of course tea. Because it was eaten at a high dining table rather than the low tea table and sometimes taken standing up or sitting on high stools, it was termed High Tea. It is considered a full meal, served around 5-6 p.m. The term was usually associated with members of the working class.
In fact, High Tea had a low enough reputation that many people of wealth took a meal that was remarkably similar to High Tea but referred to it as "supper and tea" and other euphemisms to avoid association with the working classes.