Charging moves charge, it never makes any

Rub a rubber rod with wool and the rod ends at $-6$ nC. The electrons came from the wool, so the wool ends at $+6$ nC, and the pair still totals what it did before contact: zero. That is the whole content of conservation, and it turns most charging questions into arithmetic you cannot get wrong.

1. Friction. Rubbing two different materials moves electrons from one to the other. Which way depends on the materials, and the two objects always end with equal and opposite charges.
2. Contact. Touch a charged conductor to a neutral one and the excess spreads over both. For two identical spheres the charge splits evenly, so $+8$ nC touched to $0$ leaves $+4$ nC on each.
3. Grounding. Ground is a large, nearly neutral reservoir. Electrons move to it or from it through the wire, and the object ends up neutral. Nothing was destroyed; count what left through the wire.

A statement like "the rod gained $-6$ nC that was not there before" is the tell. It is an accounting error, and the fix is to name the other side of the transfer.

Bring a positively charged rod near a neutral object. Nothing about the total charge changes, and the charge already inside the object rearranges: electrons shift toward the rod, leaving the far side positive. Now compare the two contributions.

$$\text{near side: opposite sign, smaller } r \quad\Longrightarrow\quad \text{attraction wins.}$$

The far side is repelled, and it is farther away, and $1/r^2$ makes that difference decisive. So the object is pulled in. This works for a scrap of paper, a stream of water from a tap, and an uncharged conducting sphere.

Two details matter. In a conductor electrons move freely and travel a long way, so the separation is large. In an insulator such as paper the electrons stay with their molecules, which merely stretch and align, and the separation is tiny but there is a lot of it. And in both cases the net charge is still exactly zero: only the arrangement moved.

The sequence matters and the order is the whole trick. Start with a neutral conducting sphere and a positively charged rod.

1. Bring the rod close without touching. Electrons pile up on the near side; the far side is left positive. Net charge on the sphere: still zero.
2. Ground the far side, with the rod still in place. Electrons flow up from ground to the sphere, drawn by the rod. Net charge on the sphere: now negative.
3. Remove the ground wire, still with the rod in place. The extra electrons are trapped.
4. Remove the rod. The charge redistributes over the sphere, which is now permanently negative.

Notice the result: charging by induction leaves the object with the sign opposite to the charging rod, and the rod itself loses nothing. Skip step 2 and you have polarization rather than charging, with the sphere neutral again the moment the rod leaves. Remove the rod before the ground wire and the electrons drain straight back out.

The material is not a detail; it decides the outcome of every scenario above.

In a conductor, charge carriers move freely through the material. Excess charge spreads out and, at equilibrium, sits on the outer surface, as far apart as mutual repulsion can get it. Touch two conductors together and they share.

In an insulator, charge stays where it was put. Rub one end of a plastic rod and only that end is charged; the other end stays neutral however long you wait. Touching an insulator to a charged object transfers charge only at the point of contact.

So "read the material first" is a working instruction. Two identical metal spheres share charge evenly on contact. Two identical plastic spheres do almost nothing at all.