JCR elections are an exciting period where you can run for any JCR positions (if eligible).
A weeklong nomination period is issued, where you can sign up to run for a role and submit a manifesto. Then comes a week of campaigning, involving posters, block runs and whatever else creative you can think of to swing voters in your favour. Then hustings, where you give a short speech and are grilled by your fellow students, before finally a vote is issued and the winners are announced.
You can view the available JCR positions here.
All roles are governed by a series of bye laws. You can read them here.