There are currently seven counsellors of state - the Queen, the first four adults in the line of succession (William, Harry, Andrew, Beatrice), Anne and Edward.
Anne and Edward were added in 2022, mainly to avoid any need to call on Harry and Andrew to act as such. They were appointed for life and so won’t get displaced when any of the children ahead of them come of age.
In other words, the same status that “the Queen Mother” had when her husband King George VI died and her daughter became Queen Elizabeth II.
(“You Know You’re Getting Old When…” you use a term like “the Queen Mother” and expect everybody to know exactly who that is, despite the fact that she died 22 years ago.)
Here’s a good place to ask: is the “Queen” in “Queen Mother” referring to QEII or her mother? That is, if QEII had been a boy, would the Queen Mother have been called the “King Mother” instead?
Edited: Is it more like “Queen, Mother” or “Queen-Mother”?
She was a former Queen who was mother of the current monarch. « Mother » is used here in an adjectival sense, like « General » in « Attorney General »
She preferred it over « Queen Dowager ». It was an inspired choice of new terminology. « Dowager » is an old and fusty term about the nobility. Instead, she was identifying herself as the nation’s granny.
If Elizabeth II had been a boy, the widow of George VI would still have been the Queen Mother (and Queen Dowager). But she wouldn’t usually have been called that. The only reason she was routinely called ‘the Queen Mother’ was to avoid confusion with the new Queen. She would otherwise just have been called ‘Queen Elizabeth’, in the same way that the previous widowed queen (her mother-in-law) had been ‘Queen Mary’ from 1937.
Camilla is currently just ‘The Queen’. If she is widowed, she’ll become ‘Queen Camilla’. Only when her full titles are used (which will be almost never) will she also be called Queen Dowager. Whether she would also be called Queen Mother is an interesting question, for which there is no precise precedent, although there have been childless Queen Dowagers who have not been called that. Probably less confusing if it wasn’t used, especially as it would make no difference to her legal status.