What exactly is a charge?
This post is more about wondering about what a charge is than an explanation of it.
In physics, you will come across charges in electrostatic or electromagnetic fields. Or electric charge on some conductor. Or the effects of moving charges in an electric field. Also the charge on a proton and electron. (And on neutron too).
As Wikipedia defines it:
Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.
You know the other things too. There are two types of charges. Positive and negative. And you know the interactions between them. Like charges will always repel each other and opposite charges will always attract each other.
But that is not important for our consideration here. Note what the scientific world says about the charge. It is a physical property of matter. Now consider those words.
Before you go on to study about the equation of force between the charges, or any of other things, wonder about this property called charge.
What is it? Experiments show that charges in our universe come in a minimum small size (quantized) denoted by e. That is an electron is said to have -e and a proton is said to have +e charge. If you imagine going on the atomic scales, what do you think is giving these electrons and protons this e? Is this due to their spin? Due to their vibrations? Or is it something else?
Explore more about this question and you will find the reason behind why it is called a physical property of matter. On this path of exploration, you will also come across more physical quantities that you must wonder about which scientists are having a hard time understanding. But they all are trying. And so should you.