Have you ever wondered what the small hole in a toilet is?  It’s a siphon jet.  Toilets work by gravity.  The extra hole acts as a siphon to increase the flow of water into the toilet.  This action aids in emptying the toilet faster.  Personally I didn’t understand it’s function until recently.  Our toilet kept emptying slowly.  It wasn’t until after we did a deep clean of the toilet until it started to empty normally.  

Timothy