KittySnickers

So I am creating a fantasy world for a book that I am trying to write. However, my world is a planet and I need it to work in real world science. I love science, particularly physics and planet science but my brain is about the size of a walnut, so though I enjoy it, I struggle to understand it a lot of times. I have a few questions and I was hoping someone could give me a simple answer to them. Questions about the Poles. I know that the poles are to do with the axis of Earth and the magnetic poles but my questions are. Does a life supporting planet need poles and why? Do the poles have to be cold? Do they both have to be cold? Questions about the planets core What are the workings of the planets core? What kind of things can make up a life supporting planets core? Rotation of the star Currently my planet is arid in the south west - tropical in the west - temperate cold in the north west - cold in the north - tropical in the east and temperate in the south and south east. How would this affect the planets star? My planet has two moons, one large, one small, how would this affect the tides? Thank you in advance and please use small words.