What is an atom called that has a positive or negative charge as a result of gaining or losing electrons?
An atom that gains electrons now has a formal negative charge, and is said to have been REDUCED. On the other hand, an atom that loses electrons is said to have been oxidized in forming a positively charged species.
Of course loss or gain of a formal negatively charged particle, the electron, result in a change in the electric charge of the starting material. This process is a formalism in that we use the idea of electron loss or electron gain to help us write redox equations, in which electrons are formally transferred between reactants.