Ions are electrically charged particles, meaning, that whenever any type of atom loses or gains electrons it is forming a new type of structure, or ion.
Metal atoms form postive ions, Non-Metals form negative ions.
The strongest type of bond that can occur between two ions, when they are oppositely charged, are Ionic Bonds. The most commonly known ionic bond is seen in Sodium and Chlorine, which when combined give us NaCl or Sodium Chlorine, aka Salt.
+1 charge = Group 1, Metals
+2 charge = Group 2, Alkali Metals
-1 charge = Group 17, Halogens
Provided is a periodic table marked with the charges for each group.