A system uses Voter Initiated Elections if the voting members can trigger an election at any time without having to pass through some intermediary body first.
In the context of Weighted Direct Democracy this would likely be designed such that an election is triggered if some percentage of all live voting weight is used to signal that an election should occur. Making the percentage higher or lower creates a tradeoff between more voter control and accountability on the lower end, and more simplicity and delegation on the higher end.