The Church of England practices infant baptism but when a child is old enough to take vows for themselves, usually in their early teens, they are confirmed by a bishop and can then be admitted to holy communion. Unlike baptism, confirmation is not recorded in a parish register, but records can survive - such as this card recording the events for Doris Sutherland Thomas at Tring Parish Church in 1910.
In this example it is clear that Doris had not been baptised as an infant, but had decided to join the church at the age of 18. She had undoubtedly attended confirmation classes, almost certainly with other candidates, led by the vicar, Henry Francis, and when it was realised she had not been baptised as a child a baptism was carried out a few days before the confirmation service.
For information on Doris's family see