Iterations
An Iteration is the period in which your team builds a selection of stories. Betterplan knows at most one active iteration at a time. It decides what appears on the Iteration Board, and with every completed iteration Betterplan learns how many story points your team delivers (the velocity, see Estimating).
Iteration Board
The Iteration Board is the working view of the Build phase (key 3, then 1). It shows the active Iteration: every story has its own swimlane, and next to it its workitems move through three columns. The whole team sees who works on what and what is missing, without anyone asking for status.
Iterations overview
This view is being rolled out gradually. If you don't see it yet, it hasn't been enabled for your workspace.
Bugs in iterations
Defects usually turn up in the middle of an iteration, in the story being worked on. Betterplan therefore treats a bug as a workitem with a bug flag below that story (see Report and track bugs). On the Iteration Board you see it where the work happens.