Line charts depict trends. They should be used when you want to see data over a period of time.
Line charts will generally show how you are performing as compared to previous months/quarters/years.
For this chart, you need 1 dimension and 1 measure. Any more dimensions should be used as filters. In most cases the X axis will be some kind of time field.
In the figure above, we are showing how many work orders have been created since 2019-01-01.
To edit the colour of the line on the graph, you can go to Edit → Series
To change the label on the X Axis , you can go to Edit → X
To change the label on the Y Axis , you can go to Edit → Y
If you want to show the number of orders fulfilled by different suppliers over a period of time, you will need to add Supplier to this graph and pivot it.
In the above graph you can see how different suppliers are different lines which are represented by different colours over a period of time.
For further information, please see the below video.