In the context of computer networking, Symmetrical means Upload/Download speed are working at the same speed. Asymmetrical meaning Upload/Download speed has been configured working in different speed.

VIP = Symmetrical because upload and download same speed.
Unifi Advance/Pro = Asymmetrical because Download speed faster than upload.

Usually household users use less upload bandwidth while some business users need high speed symmetrical broadband to host files/website/emails in-house.