If your toilet leaks whenever you flush it, this is an indication that a repair is needed immediately.
Usually, the problem is that the wax bowl ring needs to be replaced.
This is a job best left for plumbers.
This is a dirty job that involves removing the toilet from the floor.
The plumber will turn off the water supply to the toilet and then remove the toilet from the bolts that hold the toilet to the floor.
Because these bolts can become extremely tight, the plumber may need to remove the toilet from the bolts with a hacksaw.
Once the plumber removes the toilet, the old wax bowl ring will be removed, and a new one installed.
Last step is to make sure that the toilet is then situated firmly on the bolts.