Background hits are sent when an app is in background. Customers can use Virtual Report Suites to discard these hits from reporting. However, there is a setting in Analytics Admin Console where these hits can be disabled permanently. This KCS talks about how these hits can be disabled and how processing is affected by this setting.
Few years back, Analytics started processing background hits in reporting. That means, the processing will affect visits and visitors data. In order to prevent background hits from reporting, use Virtual Report Suites. More information here.
There is a separate setting for disabling background hits in the report suite. Background hits processing can be disabled/enabled by going to Analytics Admin Report Suites Edit Settings App Management App Reporting. By default the setting is enabled.
Background hits in data fee data can be identified by using customer_perpective column where the value of a background hit will be 1. In the url query string, the value is cp=1.
If background hits are disabled, visit_num and visit_page_num will be set as 0, which tells the processing servers to not to include the hits in reporting. On the reporting side, a look up is done once per 24 hours, if those background hits needs to be ignored. So, the changes will affect in reporting only after 24 hours past the setting is changed.