Electric charge is the physical property of matter.
There are two types of electric charges: positive and negative. Like charges (positive and positive, for example) repel, and unlike charges (positive and negative) attract. The most common charge carriers are the positively charged proton and the negatively charged electron. An object is negatively charged if it has an excess of electrons.
As per the International System of Units (SI), the unit of electric charge is coulomb, which is equivalent to about 6.242×1018 e. In electrical engineering, the unit is seen as ampere-hour (Ah), and, in chemistry, it is common to use the elementary charge (e) as a unit.
By convention, the charge of an electron is -1, while that of a proton is +1. The quantity of electric charge can be measured with an electrometer.
The study of charged particles, and how their interactions are mediated by photons, is called quantum electrodynamics.