A fundamental physical property held by various particles, most notably electrons
Electric charge is a fundamental physical property of different particles. Each particle has a charge which is either positive, negative, or neutral (also called having no charge). Electrons have negative charge.
Charged particles exert a force on each other. Like charges repel, opposite charges attract.
The motion of charge is electric current. By convention, we refer to current as flowing in the direction positive charges are flowing. Since electrons have negative charge, electron flow is opposite from current flow. This has minimal significance for most purposes.
In some cases, an imaginary particle called a "hole" is posited. A hole has positive charge. In physical reality, a hole is the absence of an electron. It is sometimes useful to model this absence as a particle.