Border Gateway Protocol (BGP) is a routing protocol, which establishes routing between ISPs. ISPs use BGP to exchange routing information between Autonomous Systems (ASs) on the Internet.
BGP peers (also referred to as neighbors) are BGP enabled devices that are directly connected through an established TCP connection. The BGP dynamic neighbors allow peering to a group of remote neighbors defined by a listen range. BGP neighbors can be created without statically configuring them.
A BGP peer group groups the BGP neighbors sharing the same outbound policies together. A peer group allows you to group the policies which can be applied to individual peers thus making efficient update calculation along with simplified configuration.