Sodium chloride is a naturally occurring chemical compound with the formula NaCl. It consists of two different ions. The sodium ion (Na) is positively charged due to the loss of an electron. The chloride ion (Cl) is negatively charged due to the addition of an extra electron. The two ions interact with each other via an ionic bond.
At this point you need to understand that there are two basic types of chemical bonds, ionic and covalent. Covalent bonds are the types of bonds where two different atoms share two or more of their electrons with each other to become bonded together. Depending on how closely these electrons are shared, covalent bonds can vary in strength depending on the types of atoms involved. Ions are a different story, though. Ions are charged atoms, and they bond to one another electrostatically via those charges. Since opposite charges are greatly attracted to each other, ionic bonds are very strong. As a result, ionic compounds tend to form crystalline salts in the solid form that are highly structured. These lattice structures are highly ordered spacial networks of the ions in three dimensional space. Due to these highly stable crystal structures, it takes a lot of energy to disrupt these crystalline networks and convert the solids into liquids. As a result, ionic salts like NaCl have very high melting points (the melting point of NaCl is 801 degrees C).