Do you remember when you were learning English and your teacher asked you to find out the meanings of different words? Semantic search is a bit like that. It's when a computer tries to understand what someone means when they type words into a search engine.
Let's say you want to search for "where to find ice cream". In the past, search engines could only match the words "where," "to," "find," "ice," and "cream." But semantic search is smarter. It understands that you're probably asking for places to buy ice cream instead of just a definition of the words in the question.
So, it will try to look for web pages that are about where to find ice cream shops or maybe even ice cream recipes. The computer uses artificial intelligence and natural language processing to figure out what you mean by the words you type.
In short, semantic search tries to understand what people mean when they search for something, instead of just matching keywords.