what difference between voxel layer and obstacle layer ?

edit

When I watch this video here, it explains them at 26:00 sec. Then I opened them in my robot and found them is different.

The local_costmap_params.yaml:

local_costmap:
  global_frame: odom
  robot_base_frame: base_link
  update_frequency: 20.0 
  publish_frequency: 20.0
  resolution: 0.05
  static_map: false
  rolling_window: true
  width: 10.0
  height: 10.0
  footprint_padding: 0.0

  plugins:
    - name: obstacle_layer
      type: "costmap_2d::VoxelLayer"
    - name: inflation_layer
      type: "costmap_2d::InflationLayer"

  inflation_layer:
    inflation_radius: 0.3
    cost_scaling_factor: 3.0
    inflate_unknown: true

And global_costmap_params.yaml

global_costmap:
  global_frame: map
  robot_base_frame: base_link
  update_frequency: 20.0 
  publish_frequency: 20.0
  resolution: 0.05
  static_map: true
  rolling_window: false

  plugins:
    - name: static_map
      type: "costmap_2d::StaticLayer"
    - name: obstacle_layer
      type: "costmap_2d::VoxelLayer"
    - name: inflation_layer
      type: "costmap_2d::InflationLayer"

  inflation_layer:
     inflation_radius: 0.5
     cost_scaling_factor: 5.0

And costmap_common_params.yaml

footprint: [[-0.380, -0.240], [-0.380, 0.240], [0.110, 0.240], [0.11, -0.240]] #RIA-E100

obstacle_layer:
  observation_sources: scan point_cloud_sensor
  scan: {sensor_frame: laser_link, data_type: LaserScan, topic: scan, marking: true, clearing: true, inf_is_valid: true, obstacle_range: 6.0, raytrace_range: 10.0}
track_unknown_space: true
     inflate_unknown: true

My robot is Rabbot

This is a configuration for Gaitech company.

What is the issue if type: "costmap_2d::VoxelLayer" instead of type: "costmap_2d::ObstacleLayer" in local_costmap_params.yaml?

Please your opinion