Here's why:
* Coordinating conjunctions (like "and", "but", "or") directly join two grammatically equal elements.
* A semicolon can do the same, but it implies a closer relationship between the clauses than a coordinating conjunction would. The clauses are connected by a shared idea, even if they don't explicitly state the connection.
Think of it this way: a semicolon acts as a bridge between the two clauses, highlighting their connection.
Example:
* With a coordinating conjunction: *The dog barked loudly; and the cat hissed in response.*
* With a semicolon: *The dog barked loudly; the cat hissed in response.*
Both sentences convey the same meaning, but the semicolon in the second sentence emphasizes the close relationship between the dog's barking and the cat's hiss.