Does an Electron Decrease Capacitor Voltage by Adding to Positive Charge?

[anhnha]

I saw this section somewhere in the forum:

Picture 2 plates charged to a voltage V, w/ capacitance C. Of course Q = C*V. An electron is placed in between the plates & released, & it moves towards the positive plate. Said electron with its negative charge now adds to the positive charge already on the plate resulting in a decrease in the cap voltage.

Can you help me understand the bold part?
What does "positive charge" mean here? I think it should be "positive ion".

 

[Simon Bridge]

I saw this section somewhere in the forum:

Picture 2 plates charged to a voltage V, w/ capacitance C. Of course Q = C*V. An electron is placed in between the plates & released, & it moves towards the positive plate. Said electron with its negative charge now adds to the positive charge already on the plate resulting in a decrease in the cap voltage.

Can you help me understand the bold part?
What does "positive charge" mean here? I think it should be "positive ion".

while that would be a specific example of how to get a positive charge, it is not the only way.
the plate is a solid lattice made up of protons and electrons.
to be positive, it must have fewer electrons than protons.
in the model being used here, the "missing electron" is treated as an isolated positive charge that is free to move around.