When you create a parse tree then it contains more details than actually needed. So, it is very difficult to compiler to parse the parse tree. Take the following parse tree as an example:

• In the parse tree, most of the leaf nodes are single child to their parent nodes.
• In the syntax tree, we can eliminate this extra information.
• Syntax tree is a variant of parse tree. In the syntax tree, interior nodes are operators and leaves are operands.
• Syntax tree is usually used when represent a program in a tree structure.

A sentence id + id * id would have the following syntax tree:

Abstract syntax tree can be represented as:

Abstract syntax trees are important data structures in a compiler. It contains the least unnecessary information.

Abstract syntax trees are more compact than a parse tree and can be easily used by a compiler.