The Moon orbits the Earth once every 28 days, not once every 24 hours, so it doesn't show up at consistent times. Instead, the Earth rotates around as the Moon moves relatively slowly, so your side of the planet rotates away from the Moon sometimes and rotates towards it sometimes. The Moon doesn't come into view exactly every 24 hours because it's also moving, so when your side of the Earth rotates away from the Moon it has to do slightly more than a full rotation to "catch up" with the Moon.
Because of this slight difference, the Moon rises at a different time every day -- sometimes during the day, sometimes during the night.