A figurehead is someone who appears to be in charge, but who really holds very little influence. In many countries today, kings and queens are merely figureheads.
A ceremonial president or king — one installed as a symbolic head of a country, while someone else holds the real power — is one type of figurehead. If a retiring businesswoman promotes her son to be the new CEO of her company, while putting a different person in charge of running the business, the son is just a figurehead. The word figurehead comes from its original meaning, the figures carved at the front of old sailing ships.