A syntax tree, also known as a parse tree, is a visual representation of the grammatical structure of a sentence. It illustrates how words group together to form phrases and how those phrases combine to create the overall meaning of the sentence. Each node in the tree represents a grammatical element, such as a noun or verb, while branches show the relationships between these elements. Syntax trees are commonly used in fields like linguistics and computer science, particularly in natural language processing and compiler design. They help in understanding sentence structure and are essential for tasks like parsing and analyzing language, enabling machines to interpret human language more effectively.