MultiLineString features are multiple lines that behave like a single Line feature.
Creating a new MultiLineString feature.
The feature creation commands available for a feature layer depend on the capabilities of the feature class represented by the layer. Feature geometry follows OGC specifications.
You can create a feature that includes arcs, even if the data store for that feature class does not support arcs. In such cases, you can set an option that determines how the arcs will be segmented when they are saved back to the data store. See To Set Arc Segmentation Values.