There are two main kinds of strokes. Hemorrhagic strokes involve burst vessels in the brain, which patients commonly complain of “the worst headache I have ever had,” which comes on suddenly.
An ischemic stroke is a blood clot blocking flow to a part of the brain, but is not a burst vessel. This type is more common.
Most patients display a weakness on one side of the body. If you were to ask them to hold up both arms they may not be able to hold both at the same height. This is a common test EMTs will use to assess strokes. Another common symptom is sagging facial muscles on one side. They may slur words or jumble them completely but not be aware that they are doing so. They may be confused and spaced out.
As far as what it feels like, it’s a bad sign if they have that headache. It’s basically an aneurysm. Confusion and vertigo are much more common than pain.