Plasma fluid is cell free, so no red or white cells or platelets. It is mainly water and proteins and carries nutrients around with it. it can cause a clot because carries all the proteins needed to stop you loosing blood when you have a cut (as well as some on the blood vessel wall)
Water, proteins, ions, but no cells.
It’s important because it contains antibodies, which coat bacteria, viruses, other germs and allergens to help the body get rid of them. Most vaccines cause the body to produce antibodies.
There are several types of plasma. Obviously what you are asking about is the plasma in blood. The biologists can answer that one.
However in physics, a plasma is an ionised gas. As a fluid is any non-rigid structure, (physics) plasma can be “fluid” in the same way that water or air can be and can be. However, because the particles are charged, there are additional forces other than those normally associated with fluid dynamics. In any case, (physics) plasmas are made of charged particles.
Yeah, yeah, I know… you were asking about blood! 😉