A module that has been integrated into Drupal 8 core. You don't need it unless you want to use the Views Bulk Edit module.
It allows you to do actions on multiple nodes.
Without the module, views offers this:
You get select boxes for the nodes.
With the selected nodes you can now do these actions:
When you installed the VBO module you have more possibilities.
Not a lot of benefits... The module only becomes interesting when you want to use the Views Bulk Edit module. You can change any field value for all the selected nodes, with this module..