In chemistry, an ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. To form an ionic compound, there needs to be at least one metal and one non-metal. The metal element is usually the positive charge and the non-metal element is a negative charge.
Ions can be single atoms, as in common table salt sodium chloride, or more complex groups such as calcium carbonate. But to be considered ions, they must carry a positive or negative charge due to an imbalance in the ratio of protons to electrons.
Thus, in an ionic bond, one 'bonder' must have a positive charge and the other a negative one. By sticking to each other, they resolve, or partially resolve, their separate charge imbalances. Positive to positive and negative to negative ionic bonds do not occur (for a real world analogy, experiment with a pair of bar magnets.)
Some properties of ionic compounds are high melting and boiling points and good conductivity. Ionic compounds are solids at room temperature and will usually form crystals.