In theoretical terms the defination for Chemical bond is 'a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds.' The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds; or through the sharing of electrons as in covalent bonds.

In other terms, any of the interactions that account for the association of atoms into molecules, ions, crystals, and other stable species that make up the familiar substances of the everyday world. When atoms approach one another, their nuclei and electrons interact and tend to distribute themselves in space in such a way that the total energy is lower than it would be in any alternative arrangement. 

You can get the complete explaination in your NCERT books as well.