Atoms are most stable when they have a certain number of electrons around them, described as “having a full shell”. A neutral chlorine atom is one electron short of having a full shell, and a neutral sodium atom has one electron more than a full shell. Therefore, neutral chlorine will rip an electron off just about anything, causing damage, while neutral sodium will push its extra electron away, same deal. That is why they are such reactive chemicals. Once they’ve done that process they are stable.

Then, as the other poster described, they are oppositely charged, so they are attracted to each other with medium strength, but not strongly bonded, which, to simplify it somewhat, is when atoms share electrons which both of them would like to have.

Ok so my understanding is that NaCl, and other salts, are bound together by ionic bonds.

In these bonds, one element typically gives up an electron completely to the other, as opposed to covalent bonds for example, where the electron (or electrons) are actually “shared” between the atoms.

So here, sodium is happy to give up its electron and live its life as Na+, while chlorine will gladly take it and become Cl-.

Since they now are oppositely charged, they kinda stick to each other because of electrostatic attraction, but not like the atoms in a molecule would.