Web scene layers are cached web layers that are optimized for displaying a large amount of 2D and 3D features and can be viewed in Scene Viewer and ArcGIS Pro. Scene layers include 
point layers, 
point cloud layers, 
3D object layers, and 
integrated mesh layers. When sharing a scene layer, a feature layer that is used to generate the cache is also shared.
Point
To ensure fast visualization in all clients, cached scene layers are used to display large amounts of 2D and 3D point data not possible with a point feature layer. Once you add a point scene layer to your scene, you can configure it as you would any other point layer. Point scene layers are automatically thinned to improve performance and visibility at smaller scales. Automatic thinning means that not all features are displayed at small scales; as you zoom in, additional features are displayed; for example, you may use a point scene layer to display all the trees in a city.
Point cloud
Point cloud scene layers allow for fast consumption and display of large volumes of point cloud data in Scene Viewer and ArcGIS Pro 1.4 or later. You can apply smart mapping styles to point cloud scene layers in Scene Viewer. You can also configure these layers in ArcGIS Pro and publish them to ArcGIS Enterprise. Point cloud scene layers in Scene Viewer can appear different based on the symbology renderer type configured from ArcGIS Pro. Scene Viewer supports the following renderer types from ArcGIS Pro:
- Stretch
- Classify
- Unique Values
- RGB
3D object
3D object scene layers can be used to represent and visualize 3D objects, such as textured or untextured buildings that are modeled in 3D. The 3D object layer can be created from multipatch data shared from ArcGIS Pro. Furthermore, 3D object scene layers can be shared directly to Portal for ArcGIS using a scene layer package generated from ArcGIS Pro and as well as exported by Esri CityEngine 2016.0 and later.
Integrated mesh
Integrated mesh data is typically captured by an automated process for constructing 3D objects from large sets of overlapping imagery. The result integrates the original input image information as a textured mesh using a triangular interlaced structure. An integrated mesh can represent built and natural 3D features, such as building walls, trees, valleys, and cliffs, with realistic textures and includes elevation information. Integrated mesh scene layers are generally created for citywide 3D mapping and can be created using Drone2Map for ArcGIS and ArcGIS Pro 2.2, which can then be shared to ArcGIS Desktop or web apps.
For more information about scene layers, see sharing a scene layer in ArcGIS Pro.