They're directional but Amber is wrong about something.
Not all covalent compounds are polar.
CH4 definitely isn't.
Also, sometimes the polarities cancel each other out, leaving a neutral molecule
Covalent bonds are formed when two atoms share an electron pair to complete their outer most shell. In a covalent bond an electron pair is shared by two similar or different atoms. The atom which has greater electronegativity gets partial negative charge. The atom which has less electronegativity attains partial positive charge. So, molecules which have covalent bonds are polar compounds. The partial negative charge of one molecule attracts the partial positive charge of second molecule, the partial negative charge of second molecule attracts the partial positive charge of third molecule nad so on. In this way, covalent bond becomes a three dimensional directional bond.