I tried to solve the integer points of $y(y+2)=x^3+(x+3)(x+5)$ by using Sage's command
E.integral_points(). Its output was $[(0 : 3 : 1)]$. I tried that $(x,y)=(0,3)$ satisfies my equation. But what does the third number $1$ means in Sage's notation?
It means that it homogenises it and treats it as a curve in projective space.
Your question is not a mathematics question but a Sage question!
The output for E.integral_points() is a list of points, in your example a list with one element. If you extract that point like this:
then you can view it in a different way: