Plot bands and plot lines can be used within charts to add some highlighting to the overall chart. Both of them have the options for color, events, id, label, and z-index. In general, these lines and bands are always perpendicular to the axis they are defined with. Polar charts or gauge can also have data separators, but these behave differently, as there is no axis to have the separator perpendicular to.
Additional information can be found directly on the Highcharts page.
For the example chart configuration in this article the Highcharts-Editor is used.
There are two different possibilities to separate the visualisation within the chart:
They can be added and configured at the axis configuration under "Advanced":
The "value" has to be set in axis units!
The "from" and "to" values have to be set in axis units!
JSON for xAxis configuration
Full chart element configuration code