Anna, the 7th Duchess of Bedford, introduced afternoon Tea in England in the year 1840. Lunch had become a "skimpier" meal, so of course, the Duchess would become very hungry around 4 o'clock in the afternoon, far from when dinner was served around 8 o' clock in the evening.
The Duchess found taking an afternoon snack to be such perfect refreshment that she soon began inviting her friends to join her. She found a light meal of tea (usually Darjeeling) and cakes or sandwiches was the perfect balance.
While there are no strict rules, the standard spread for Afternoon Tea includes sandwiches, cakes, and scones or tea cakes, sometimes substituted with pastries, petits fours, or biscuits.