Image Bob uses firstname.lastname@example.org to email@example.com for receiving all the bank statements.
He can also use firstname.lastname@example.org to email@example.com for receiving invoices.
In that case, Bob can easily find the emails related to banking statements and invoices if he searches the "+" in filters. He also can search "red" to look for banking statement related emails only.
For now, the virtual aliases are unlimited, and you do not have to set them up in settings. All the incoming emails with your user name "+" will be automatically saved in your inbox.