... like I'm 5 years old
Imagine you're sitting by a pond, and you toss a stone into the water. What happens? You see ripples spreading out from where the stone landed, right? Now think about the moon as a gigantic stone and the Earth's oceans as that pond. When the moon "tosses" its gravitational pull into the ocean, it creates a bulge of water - or a high tide. On the side of Earth opposite the moon, there's another high tide. This happens because Earth is also spinning while the moon's gravity is pulling on it, causing the water to be flung outwards. As the Earth continues to spin, the place you're standing on will move through both of these bulges, causing two high tides and two low tides each day.
Think of it like a seesaw. When one side is up (high tide), the other side is down (low tide). And just like you and a friend can keep a seesaw moving up and down, the Earth's rotation and the moon's gravity keep the tides moving.
... like I'm in College
Expanding on the basic concept, the gravitational interaction between the Earth and the moon is not the only factor affecting the tides. The sun also exerts a gravitational pull on Earth's waters, although its influence is about half as strong because it's much further away. When the sun, moon, and Earth are aligned (during a full moon or new moon), the sun's gravity enhances the moon's, causing higher than average 'spring' tides. During the first and third quarter moon, the sun and moon's gravitational forces work against each other, resulting in lower than average 'neap' tides.
Also, the shape and depth of ocean basins and the rotation of the Earth itself can affect the magnitude and times of high and low tides. For example, in the Gulf of Mexico, there is only one high tide and one low tide each day.
Let's use Lego bricks to model the Earth and moon, and a blue sheet to represent the ocean. Place the Earth model in the center of the sheet and the moon model some distance away. Pull the sheet towards the moon model to mimic the gravitational pull, creating a "bulge" - that's a high tide.
On the opposite side, stretch the sheet away from the Earth model, creating another bulge. As the Earth model rotates, the bulges move around it, representing the changing tides. Now introduce a smaller Lego model as the sun, a little further from your Earth setup. Notice how its added "pull" on the sheet can increase the size of the bulges during certain alignments?
Just remember, our Lego setup is a simplified model. In reality, the ocean's depth and shape, along with Earth's rotation, also play a part in creating the complex phenomenon of tides.
... like I'm an expert
While the basic and intermediate explanations capture the general principles of tidal phenomena, the actual dynamics are far more complex and involve several interconnected factors.
Precisely, a full understanding of tides requires delving into the field of tidal dynamics which combines the principles of celestial mechanics, fluid dynamics, and Earth's rotation. The equilibrium theory of tides assumes an Earth covered completely by a uniformly deep ocean and neglects the rotation of the Earth. This simplified model illustrates the principle of tide generation, especially emphasizing the role of gravitational forces from the moon and the sun.
However, the dynamic theory of tides takes into account the depth and shape of oceans, continents, Earth's rotation, and the viscosity and temperature of water. This model yields a more accurate match to actual tidal patterns. It also explains why the highest tides in the world occur in the Bay of Fundy in Canada, a location with unique physical characteristics.