Difference between agile scrum and kanban?

For scrum, there is a fixed sprint length of 1 – 4 weeks but on the other hand, kanban aims to achieve continuous flow i.e. there is no set time. This also means that at the end of the sprint, a scrum team would have developed a working software that could be shipped. For kanban, there is no predetermined release dates.
There are also 3 prescribed roles in scrum (scrum master, product owner and scrum team) whereas in kanban there are none.
For scrum, the team tries to not change the scope of the sprint unless there has been a feedback from the stakeholder(s) that what they are working on is wrong or not as important. Compared to scrum, the kanban workflow is very flexible to changes i.e. any new work can be added in.