For example, when King Charles III passes away, Prince William will become the king.
Next in line would be his son, Prince George.
The Succession to the Crown Act from 2013 changed some of the rules regarding ascension to the throne.

After the coronation, Camilla’s official title became just Queen Camilla.
Queen Elizabeth II’s mother, Queen Elizabeth, was also a queen consort.
After Elizabeth II was crowned queen following her father’s death, her mother became the queen mother.

The reason is because Camilla is not Prince William’s mother.
The prime minister and cabinet would have to agree on the titles in that scenario.
