Okay kiddo, have you ever seen a ball? If you spin the ball really fast, it starts to bulge out in the center. This is because the spinning motion makes the middle of the ball push outwards.
Now imagine the Earth like a huge ball spinning in space. The Earth spins around its axis (an imaginary line going through the Earth from the north pole to the south pole), and this spinning motion causes something called a "pole tide".
Basically, the Earth is not a perfect sphere - it bulges out a bit around the equator. And because the Earth is not perfectly symmetrical, it can wobble a little bit as it spins. This wobbling causes the water in the ocean to move around and gather on one side of the Earth, making the sea level rise.
The pole tide happens twice a day, and the difference in sea level can be incredibly small - only a few centimeters in some places. But it's still important, because it can affect ocean currents and weather patterns.
So, in short, pole tide is when the Earth wobbles as it spins, causing a very slight rise and fall in the ocean's surface every day.