A tonic-clonic seizure is a disturbance in the functioning of both sides of your brain which makes it a generalised seizure. This sends out signals to your muscles, nerves, or glands which can make you lose consciousness and have severe muscle contractions. I have had these for years and they make you feel sore all over, I have even slept solid for 28 hours afterwards!

This type is what most people think of when they hear the word "seizure." An older term for them is "grand mal." As implied by the name, they combine the characteristics of tonic seizures and clonic seizures.

The tonic phase comes first: All the muscles stiffen. Air being forced past the vocal cords causes a cry or groan. The person loses consciousness and falls to the floor. The tongue or cheek may be bitten, so bloody saliva may come from the mouth. The person may turn a bit blue in the face.
After the tonic phase comes the clonic phase: The arms and usually the legs begin to jerk rapidly and rhythmically, bending and relaxing at the elbows, hips, and knees. After a few minutes, the jerking slows and stops. Bladder or bowel control sometimes is lost as the body relaxes. Consciousness returns slowly, and the person may be drowsy, confused, agitated, or depressed.
These seizures generally last 1 to 3 minutes.
A tonic-clonic seizure that lasts longer than 5 minutes needs medical help. A seizure that lasts more than 10 minutes, or three seizures without a normal period in between, indicates a dangerous condition called convulsive status epilepticus. This requires emergency treatment.

Tonic CLONIC seizures were originally known as a Grand Mal seizure. It's the most sever seizure.

Grand mal seizures have two stages:

Tonic phase. Loss of consciousness occurs, and the muscles suddenly contract and cause the person to fall down. This phase tends to last about 10 to 20 seconds.
Clonic phase. The muscles go into rhythmic contractions, alternately flexing and relaxing. Convulsions usually last for less than two minutes.
The following signs and symptoms occur in some but not all people with grand mal seizures:

Aura. Some people experience a warning feeling (aura) before a grand mal seizure. This warning varies from person to person, but may include feeling a sense of unexplained dread, a strange smell or a feeling of numbness.
A scream. Some people may cry out at the beginning of a seizure because the muscles around the vocal cords seize, forcing air out.
Loss of bowel and bladder control. This may happen during or following a seizure.
Unresponsiveness after convulsions. Unconsciousness may persist for several minutes after the convulsion has ended.
Confusion. A period of disorientation often follows a grand mal seizure. This is referred to as postictal confusion.
Fatigue. Sleepiness is common after a grand mal seizure.
Severe headache. Headaches are common but not universal after grand mal seizures.
When to see a doctor

If you see someone having a seizure:

Call for medical help.
Gently roll the person onto one side and put something soft under his or her head.
Loosen tight neckwear.
Don't put anything in the mouth — the tongue can't be swallowed and objects placed in the mouth can be bitten or inhaled.
Don't try to restrain the person.
Look for a medical alert bracelet, which may indicate an emergency contact person and other information.
Note how long the seizure lasts.
A grand mal seizure lasting more than five minutes, or immediately followed by a second seizure, should be considered a medical emergency in most people. This is also a medical emergency if the person is pregnant, injured or diabetic. Seek emergency care as quickly as possible.

Additionally, seek medical advice for you or your child:

When the number of seizures experienced increases significantly without explanation
When new signs or symptoms of seizures appear

I know those kind. I have a drug called Nayazilam that is a rescue drug and it has saved me I believe 3 times they used it from a hospital stay.