That's called the "waxing crescent".
This phase is known as the waxing crescent phase of the Moon. During this phase, the Moon appears to grow thicker each night as more of its lighted side becomes visible from Earth.
This period is known as the waning phase of the moon. During this phase, the illuminated portion of the moon visible from Earth decreases in size as it transitions from a full moon to a new moon.
A waning moon
The moon phase "waning gibbous" appears after the moon phase "full moon".It becomes the "last quarter" or "third quarter" when the lighted part is exactly 50%of the side facing the Earth.
One side of the moon (the Earth facing side) becomes fully visible at Full Moon.
After the half-moon phase, the moon's lighted side appears to grow smaller every night, transitioning towards the new moon phase where the moon is not visible in the sky. This progression is known as the waning crescent phase.
The phase of the moon that occurs between the third quarter and the new moon is the waning crescent. During this phase, the illuminated part of the moon visible from Earth decreases until it eventually becomes a new moon with no visible illumination.
The moon phase when none of the lighted portion can be seen from Earth is called a new moon. During this phase, the moon is positioned between the Earth and the Sun, so the side of the moon facing Earth is not illuminated.
The decreasing of the illuminated face of the Moon (full to new) is called "waning." (The opposite, increased illuminated area, is called waxing.)
New moon.
crescent moon
The phase of the moon that comes right after the new moon is the waxing crescent. It is when a small sliver of the moon's illuminated side becomes visible from Earth.