The Visible (all companies) option is used in various contexts. For example, when establishing a connection to an external data source or in the query details for importing master data.
If you have several companies, you normally create a connection to the external data source or a query of the master data for each company. With the Visible (all companies) option, you can use a connection created once or a specific query for all companies.
You save time by activating the option.