Toroidal Vortex, or more commonly known as vortex ring, is a vortex made from rotating fluid that is moving through the same medium. Toroidal refers to the doughnut shape that is characteristic of this type of vortex. This is formed when a spherical body of fluid moves through a stationary medium, pushing into the middle and in turn making the circumference rotate and fold onto itself.
An example of toroidal vortex are smoke rings. If you observe a smoker blowing smoke rings in the air, you will notice that the smoke is actually rotating from the inside out as it travels forward. Another example of toroidal vortex is a weather formation called microburst (or downdraft), a column of air that travels downward to the ground at high pressures. A microburst can be so strong that it can down power lines and even cause aircrafts to crash. When a microburst hits the ground, a toridal vortex forms around the point of contact.
A vortex ring state is also a dangerous situation in flying helicopters, and this can occur when three factors are present in a helicopter flight: low or no airspeed, rate of descent and applied power. When a vortex ring state happens to a helicopter, it means that the helicopter is descending (many times catastrophically) into its own downwash.