Before you begin playing with the Ion Engine simulations, it's a good idea to learn something about electric charges. There's really not much to know!
First, electric charges come in two flavors:
Most things in the world have the same number of and charges, so they are called neutral.
If something has more than it's called Positively charged.
The more extra charges something has, the bigger we draw it. So, we'll draw something with lots of Positive charge like this: