Question:  What's the difference between ions, ionic compounds, and covalent compounds?

Answer:
An ion is an atom or covalently bonded group of atoms that have electrical charge.  They do this by gaining electrons (to form negatively charged anions) or by losing electrons (to form positively charged cations).

Covalent compounds are just groups of atoms that share electrons with each other.  They're generally composed entirely of nonmetals or metalloids.

Ionic compounds occur when an anion sticks to a cation.  They stick together because they have opposite charges, and as you're probably already aware, opposite charges attract each other.