Crowning is a term that can have several different meanings depending on its context.
In one sense, crowning refers to the act or ceremony of placing a crown on someone's head as a sign of honor, authority, or achievement. This could be in the context of a royal coronation, where a new monarch is invested with regal power and glory through the placement of a crown upon their head by an official representative of the state.
In another sense, crowning can refer to the final stage or moment of completion of something, such as a construction project when the finishing touches are put in place and a ceremonial ribbon is cut to mark its "crowning" achievement.
The term could also be used metaphorically to describe an accomplishment that brings great honor or recognition, such as winning a championship in sports being referred to as a crowning achievement for the team.