1- It may be a Kohler (IMHO)=2- Improperly installed=3- someone put something in that DID NOT come out of their body naturally=4- undersized waste or vent==5- not enough volume in the flush to remove solids=
there's a back up in the system. probably where the main pipe goes to the sewer or septic.
some people flush their fish down the toilet when it dies, and the toilet is connected to the sewer.
You may have roots that have penetrated your sewer line. If you have a septic system it may be time for pumping and an inspection of your system. I am going with tree roots breaking into your sewer line though.
the toilet overflows if either the building sewer, branch line in your sewer system or trap in your toilet gets clogged.
It doesn't dissolve in your sewer drain, and clogs it up so that the house backs up.
Sometimes it will, sometimes it won't. You're taking chances if you do. Same as putting a bunch of paper towels down the toilet. Usually the toilet will back up and overflow before the lines will clog as the p-trap built into the toilet is smaller than the diameter of the sewer pipe.
Your home improvement warehouse store or bathroom contractor should have "flush-up" toilet kits (sewage ejector pump, Qwik Jon is one I have installed. These are very handy where no sewer is available for standard toilet installation. The kit consists mainly of a tank and pump that will carry waste to the existing sewer lines and misc. parts and installation instructions. You provide the toilet and PVC from tank to sewer. They run about $800-$1000 depending on your needs (toilet only, or toilet, lav, & shower configuration). These require a GFCI outlet nearby so you may need an electrician, the rest is very easy. Good luck. In addition to the installation instructions I would recommend installing a "clean-out" in your PVC, especially if you are pumping a considerable distance, in case a clog develops.
Rubber gloves and a plastic contractors garbage bag
It might be plumbed wrong -- or either your sewer is stoping up --
It will go to the sewer or a septic tank. Back then drains used to lead to the ocean. That's what happens.
Goes straight to sewer
You may need to replace the wax seal under the toilet.