Ionic bond in NaCl

You can see the formation of Sodium(+) ion.Similarly Chlorine(-) ion forms by adding one more electron to chlorine atom.These two ion formation leads to attraction, since these two are with unlike charges.Moreover in sodium ion the space (orbital) of removed electron is now empty which tends to attract the extra electron of chlorine ion leading to formation of ionic bond to form NaCl molecule.

What differs atoms from ions?

Ions are nothing but atoms with either positive or negative charge.We can make a neutral atom into a positively charged ion(cation) by simply removing electrons or negatively charged ion(anion) by adding electrons, since removing electrons the no. of protons in that atom increases when compare to electrons leading to a cation.
This ion formation in Sodium atom and Chloride atom leads to the formation of Sodium chloride molecule through ionic bond formation commonly known as table salt.
Ionic Bond in NaCl