This sketchup v-ray tutorial is based on the process to set sky with domelight and HDRI in vray 3.4 sketchup.
Dome Light produces simple, artifact-free image-based lighting with significance sampling of HDR images. This method makes light tracing and global illumination process accurate.
The VRay Dome Light belongs to a V-Ray specific light source plug-in that is applied to generate image base lighting setup.
It is available in v-ray toolbar as dome light icon. Just click on it and then click any place in the scene to arrange the dome light.
HDRI means High Dynamic Range Imaging. It is a method that creates a bigger span or range of luminance amid the light and dark areas of an image.
In V-Ray for SketchUp, the HDRI can be applied both as a background and an IBL (Image Based Lighting). If HDRI is applied as background, just load it in the Environment Rollout/Background. If it is required to use it as an IBL, then just load this HDRI in the GI (Skylight). It will transform to a light source then to illuminate the scene.