This is a term relating to Data, Information and Knowledge. When you string words together to form a sentence, you use 'semantics' to understand the meaning of the sentence. "Semantic" is the meaning behind data.
For example "Fruit flies like an orange"
Does this mean that insects known as Fruit flies like to eat an orange?
Or does is mean that fruit will fly through the air like an orange?
Unless you understand the context (semantics) of the sentence you cannot know the correct interpretation.
This is why computers often make such a hash of language translation!
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Semantics