Language is structured by semantics.
Language semantics are not natural, they are created by people to establish a common method to communicate. To interpret Natural Language the semantics must be known or learned.
Semantic based NLU is focus on the understanding of the language content and its usage. It utilizes information about the placement and usage of tokens/words to determine their purpose.
Semantics are encoded in word use, placement in sentence, document layout and visual elements
[bold, underline, color, font]
Additionally many semantics are associated with contextual usage of language elements
[a resume, a books cover, a title page, a business card, etc]