Hello Lina, are you looking for explanations for them in general or something in specific to Aviatrix?

BGP is Border Gateway Protocol and is a dynamic routing protocol widely used in networking (especially cloud networking).
https://www.cloudflare.com/learning/security/glossary/what-is-bgp/

CIDR is Classless Inter-Domain Routing and is what allows us to break up IP subnets into something other than the old Classful (Class A/B/C/D) subnets.
https://whatismyipaddress.com/cidr