Having your partner wrap their hands around your throat (strangulation) is both imminently dangerous, potentially dangerous for days afterward, and unless it's something you've specifically asked them to do to you, can be a huge warning sign that you should be worried about their willingness to use violence against you.
A lot of people think the big issue is that strangulation compresses the trachea and hinders breathing. That's a thing, but what's even more dangerous is the compression of the blood vessels in your neck, which can directly cut off blood flow to your brain.
Even after the strangulation is over, there are potential lasting effects—brain damage, memory loss, and confusion, which often make strangulation victims very poor reporters of their own level of injury, which means that if, say, police show up following a fight, the victim might honestly say that they don't think they were hurt very much and they feel fine.
About half the time they will have very small visible symptoms, like bruises on their neck, a raspiness to their voice, very small red specks on the skin of their neck or face, or burst vessels in their eyes. Half the time they won't.
Which is not always a great way to tell which of them, in the days afterwards, will have a blood clot travel into their brain and cause a stroke, or will experience seizures and memory issues over the next several months or years. Those things might not be spotted without specialized medical attention and tests. If you've ever been strangled, tell a doctor; it may still be putting you at medical risk.
And aside from the medical risks, there are indicators that someone who has survived being strangled by an intimate partner is at a much higher risk of being a homicide victim. That basically, the willingness to strangle as an act of aggression can signal that they are more willing and able to actually kill you.