What is the difference between the ionic bond and the covalent bond?
Covalent bonding results from the sharing of electrons between nuclei.
The modern covalent bond is conceived to be a region of high electron density between 2 positively charged atomic nuclei such that nucleus/nucleus repulsion is negated, and a net attractive force results.
On the other hand, ionic bonding is conceived to result from the transfer of electrons to form discrete positive and negative ions. The ions become bound in an electrostatic lattice in which every cation is electrostatically bound to every other anion in the lattice, and vice versa. Of course the cations/anions are repelled by like charges, but if you sum up the attractive and repulsive forces across the lattice, which may certainly be done quantitatively, a net attractive force results.
Ionic bonding is essentially non-molecular and non-directional, and results from sharing the sharing of electrons between nuclei. Covalent bonding is highly directional, and can be molecular.