You can find the current constitution here. This is the document that details how the society is run and what each member of the exec is responsible for. If you want to discover the nitty-gritty of this organisations structure, you need look no further! Its a thrilling read, I promise*.
* The executive committee of this society is in no way responsible for the consequences of reading this document. Known side effects of reading this document include boredom, drowsiness and unconsciousness. Do not read while operating heavy machinery. Always read the label.
Here you can find the handover document. This goes into significantly more detail about what and how each exec role is fulfilled. It contains within its copious pages tips and tricks for the duties and responsibilities of each role in turn. Want to know how to book rooms or format newsletters for facebook? Its all here in this document.