When a person is intubated it means that the person has had or is having a tube inserted into them for breathing purposes.
People are intubated when they cannot breathe properly on there own or cannot breathe on their own at all and intubation is commonly used to refer to the insertion of a breathing tube into the trachea for mechanical ventilation.
So if someone has been intubated they are on or have been on a breathing machine or hospital breathing ventilator.
The intubation can be a form of life support when people are having lung issues and breathing problems and sometimes a person may need to have a ventilator or intubation done while undergoing certain types of surgery.