Flexibility in planning
A kanban team is only focused on the work that's actively in progress. Once the team completes a work item, they pluck the next work item off the top of the backlog. The product owner is free to re-prioritize work in the backlog without disrupting the team, because any changes outside the current work items don't impact the team. As long as the product owner keeps the most important work items on top of the backlog, the development team is assured they are delivering maximum value back to the business. So there's no need for the fixed-length iterations you find in scrum.
ProTip: Savvy product owners always engage the development team when considering changes to the backlog. For example, if user stories 1-6 are in the backlog, user story 6's estimate may be based on the completion of user stories 1-5. it's always a good practice to confirm changes with the engineering team to ensure there are no surprises.