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.)