Simple strands are rendered using Arnold's curves primitive.

The following attributes are used, if available:

If instead, the strand has some instance shape connected, then the shape is always bent along the strand, and a single polymesh object (or group if the instance shape is a model) is created for each strand.

You can instantiate meshes and models.
The per-point attributes (like the color in the case below) are exported as constant data for each instanced object.
The per-strand-point attributes are exported as varying data (one value per curves point) only for plain curves nodes.

 

The strand orientation attribute, if available, is used:

More information can be found here: Hair / curve parametersHair Tutorial.