what is site to site VPN ?

what is customer gateway ? when it needs to configure ?

how to release the elastic ip ?

Releasing the Elastic IP we have to go Elastic IP =>select Elastic IP => Actions => Release Elastic ip addresses

explain subnet ?

Subnet means it divides the larger network into multiple smaller networks, Each subnet operates as an independent network, allowing for more efficient routing and management of network traffic.

explain route table ?

Each VPC has a route table, it has all route information like allowed private/public subnets how to communicate with in the VPC.