Rather than try and explain in words, when diagrams work much better, I will direct you to the Palomar site for an explanation. http://daphne.palomar.edu/jthorngren/tutorial.htm

They are linked - while Earth moves around the sun every 365(.25) days, and the Earth rotates around its own axis every 24 hours, the axis itself is more or less fixed in place (i.e. if you were to look at the Earth from great distance, it would always tilt in the same direction). This means that the orientation of the axis in relation to the sun will change over time - returning to its original position after a year. The orientation of the axis in relation to the sun is what causes seasonality on Earth, hence the seasonal cycle is a year.