Why is the earth tilted? How does this tilt effect our seasons?
Tilt comes from an ancient collision.
From what I have read a long time ago, there were 2 planets in very similar orbits. One planet is moving faster than the other and it was a matter of time till a cosmic collision happens.
The collision causes Earth's core to fuse with the other's and thus we have an iron core. The collision also tilted the axis of rotation.
Tilted axis gives rise to the season experienced by most countries away from the equator.
As you can see from the diagram, axial tilt will cause certain parts of the world to face the Sun more than others only at certain parts of the year.
Hope that clears things up.