covalent bond (molecular bond): a chemical bond that involves the sharing of electron pairs between atoms.
1. Non-polar covalent bond: the electrons are shared equally between atoms
ex: CH₄ (methane)
2. Polar covalent bond: the electrons are not shared equality between atoms
ex: H₂O (water)
Ionic bond: a chemical bond formed between two ions with opposite charges
ex: NaCl (sodium chloride)
To know the difference between ionic and covalent bonding, one must first understand the chemical difference between sharing electrons and being attracted by charges to one another.
Every atom wants to fulfill the octet rule, or, getting to a stable 8 electrons in its outermost shell. (Having 8 valence electrons)
Atoms in covalent bonds do this by sharing electrons. A good analogy to express this would be if there was a toy that we both wanted, but there was only one of them. Instead of you or I having it to ourselves, we would share. This is what atoms in covalent bonds do.
Atoms in ionic bonds do this by transferring electrons. Sodium loses an electron and chlorine gains an electron (becoming chloride). This is like you taking the toy to yourself. Now because sodium is now a positive ion and chloride is a negative ion, the two come together because opposite charges attract.
I really hope this helps!
Best wishes!:)