A parse tree is a visual representation of the syntactic structure of a sentence according to a specific grammar. It breaks down the sentence into its components, showing how words and phrases are grouped together. Each node in the tree represents a grammatical element, such as a noun phrase or verb phrase, illustrating the relationships between them. In computer science, parse trees are used in compilers to analyze and interpret programming languages. They help in understanding the structure of code, enabling the compiler to generate the appropriate machine code. This process is essential for translating high-level programming languages into a format that computers can execute.