When you are walking on the street and see your reflection on the shop windows, it is because the light doesn’t pass through the glass completely. It’s hitting the front surface of the glass and bounces off it. Some light even passes through the front surface, but bounces off internally when reaching the back surface, letting even less light through the glass. Not just you can’t see inside the store but because not all the light is passing through the glass, the reflections decrease the clarity and contrast of the view from the other side of the window too.
When you are wearing your sunglasses and the light coming from the side or behind you creates a reflection of your own eyes on the back surface of the lens, it can be very distracting and even dangerous when driving.
Anti-reflective coating is practically a special type of lens enhancement. A coating applied to the front and back surface of the lens helps improve the transmittance of the light through the lens, reducing glare and reflections, improving vision and even the cosmetic appearance of the spectacles.
You can observe these coatings applied to different optical devices, such as binoculars, microscopes, and even the camera of your phone. The bluish-green or purply reflection you see is the coating on the camera lens, that reduces glare and improves the clarity of the photograph or video you are taking.