There are three states in matter: solid, liquid and gas. The fourth state is called plasma. But it is generally not included. It is obtained by heating a gas until the atomic electrons are eliminated from the atomic nucleus. Hence in the state of plasma only the atomic nucleus exists because all it's electrons are disassociated from it. The nucleus is positively charged. And as they plasma contains only the nucleus, it is also obviously positively charged. Removal of electrons is called ionization and hence electrons dissociate from the nucleus here, plasma is said to be in an ionized state. Plasma does not have a definite shape or volume. Plasma is present in stars, lightning and fluorescent bulbs.