What is the primary purpose of a "head" in jazz compositions?

The primary purpose of a "head" in jazz compositions is to serve as the main theme introducing a piece. The head constitutes a recognizable melody that sets the foundation for the entire performance. It is typically presented at the beginning of a tune, establishing key melodic and harmonic elements, which will be revisited later in the arrangement, particularly after improvisational solos. This thematic statement is essential as it gives listeners a point of reference and familiarity within the performance, allowing for the exploration of improvisation that follows. The head often captures the essence of the composition, making it a crucial aspect of jazz music's structure.