Zeroes of the polynomials are the x coordinates of the point where the graph of that polynomial intersects the x-axis.
If the value of p(y) at y = k is 0, that is p (k) = 0 then y = k will be the zero of that polynomial p(y).
For example, consider a polynomial.
When x=1, the value of p(x) will be equal to
Since p(x) =0 at x=1, we say that 1 is a zero of the polynomial