I only learnt this recently, but even though we are tidally locked with the moon and only see one face from the earth, different parts of the Earth see that one face of the moon differently depending on where you are standing on Earth. Here in the southern hemisphere, the moon looks "upside-down"

The moon is tidally locked with Earth. That means that the same side of the moon is always facing us. However, over the course of its month-long cycle around the earth, the light from the sun illuminates different parts of the Moon, which is why only half of the Moon is visible right now. A full moon is when the entire visible face is illuminated by sunlight, and a new moon is when all of the sunlight is hitting the side that we can't see.