What is a bond?
The modern chemical bond is conceived to be a region........
The modern covalent bond is conceived to be a region of high electron density between 2 positively charged atomic nuclei, such that internuclear repulsion is negated and a net attractive force results.
This goes back to our earliest descriptions of bonding in chemistry. Ionic bonds result from the transfer of electrons to form discrete positive and negative ions that are of course attracted to each other. On the other hand, covalent bonding is conceived to be the sharing of 2 electrons between nuclei. This sharing creates that region of electron density, such that an equilibrium distance is maintained between the bound nuclei; and of course this equilibrium distance is the bond length.