An algebraic integer is just like a regular number, but it might not be a whole number like 1 or 2 or 3. Instead, it might be something like 1/2 or 5/3 or even square roots like √2 or √3.
But the most important thing about an algebraic integer is that it can be made by adding, subtracting, multiplying, and dividing whole numbers, and also by taking square roots! This is really cool because it means we can still do lots of math with these numbers, just like regular whole numbers.
For example, if we have the algebraic integer √2 + 1, we can do things like add another number to it, like 3, to get √2 + 1 + 3 = √2 + 4. We can also multiply it by another number, like 2, to get 2(√2 + 1) = 2√2 + 2.
So, algebraic integers might look a little bit different than whole numbers, but they can still be added, subtracted, multiplied, and divided like whole numbers.