The phenomenon you're describing is called waxing.

Here's why:

* Lunar Phases: The Moon doesn't emit its own light; it reflects sunlight. As the Moon orbits the Earth, the angle at which we see the illuminated portion changes, creating the different phases we observe.

* Waxing: This term refers to the period when the illuminated portion of the Moon appears to be growing larger.

* Waning: Conversely, this term refers to the period when the illuminated portion of the Moon appears to be shrinking.

So, when you see more of the illuminated portion of the Moon today than yesterday, the Moon is in a waxing phase.