Plasma even though considered to be among the 4 fundamental phases of matter has signif different properties from the other three phases (solid, liquid and gas). Unlike the other three, plasma doesn't naturally exist on the Earth under normal surface conditions, and can only be made under artificial conditions from neutral gases. Plasma in simple words is a collection of ionized particles. An ionized gas is plasma. It's a collection of electrons with positively charged gaseous ions. It is associated with the interior of the sun and other stars. One another marked difference is that unlike the common solid-liquid-gas phase transitions, phase transitions with plasma do not take only by varying pressure and temperature. Plasma is generated by ionizing a gas using a strong electromagnetic field and/or heating the gas to fantastically high temperatures (so high that it could melt any ordinary container; for this reason magnetic fields are used to confine hot plasma). Hope this helped :)
