Pre-Elizabeth, Victoria was queen. She too held the roles of leader and head of state, no? The statue of Victoria outside Buckingham Palace reads "Regina Imperatrix" - Queen Emperor - so wouldn't she have been the head too? When did the Queen take over?
Assuming you're talking about the current queen of Britain, Elizabeth Alexandra Mary Windsor, she became more important than the king once her father, George VI, died.
Elizabeth's husband, Prince Philip, is not a king; as a royal himself but not a member of the British royal family, he's styled His Royal Highness The Prince Philip, Duke of Edinburgh.
Victoria similarly ascended the throne as a queen, though she was only 18 when her uncle William IV died, and similarly married outside the British royal family, to Albert of Saxe-Coburg and Gotha, who was also created a prince consort.
Assuming that the line of succession for Elizabeth works as planned, her son Charles, Prince of Wales, will be the next king of Great Britain; his heir apparent is his son Prince William, the duke of Cambridge.
Does that make sense? Elizabeth is more significant than Philip because she, not he, is the monarch.
To add to what u/jschooltiger said, there are two kinds of Queens; Queens Regnant, and Queens Consort. Queens Consort are not the monarch, they're just married to the King so they get to be called Queen. Queens Regnant, on the other hand, inherit the throne from their father(/great-uncle/brother/sister. None have inherited it from their mother, though of course it could happen one day). Their husbands are not called Kings, but Prince.
So basically, it's a matter of sexist nomenclature; a man who inherits the throne is called King, a man who marries the Queen is called Prince. A woman who inherits the throne is called Queen, a woman who marries the King is also called Queen.
Elizabeth II is Queen Regnant because she is the oldest child of King George (who had no sons). Her husband isn't King Philip, he's Prince Philip.
Similarly, Victoria didn't become Queen by marrying the King, she was just their heir to the throne, so when King William IV died, she ascended to become Queen. Later she married Prince Albert.
Other Queens Regnant of Britain include Elizabeth I, Mary I, Anne, Victoria, and Mary who was co-monarch with her husband William of Orange (technically Mary II, but they tend to be referred to as William and Mary). Also arguably Matilda.
All the other Queens were just the wives of Kings, and so don't get numbers or generally much attention historically.
In future, when, say, Prince William becomes King William V, his wife will be Queen Catherine (not Queen Catherine V or III or whatever). She wouldn't be Queen-Regnant though like Elizabeth II is, just Queen-Consort.