When I call s3 bucket from EC2 instance the call will happen via public internet or private with call within AWS?

The Amazon S3 endpoint is on the Internet. Therefore, the request will go on the "Internet" via a Public IP address. However, it stays within the AWS network, so it doesn't hit the "wild west" Internet.

Alternatively, you can create a VPC Endpoint for Amazon S3 inside your VPC. This creates a 'short-cut' directly to S3 without going via the Internet. Communication takes place using Private IP addresses.