How does a private subnet know how to route to a NAT gateway in the public subnet

Question

Hello.  So I have been reading documentation and I am confused on the NAT gateway setup.  I get that the NAT gateway is needed in order for private subnets to access the Internet and that the NAT gateway needs to be in the public subnet.  
What I am not understanding is how does the private subnet communicate with the NAT gateway?  I am not seeing the connection because the private subnet cannot see the public subnet.  Is there a route for this in the route tables that I am not seeing?

Accepted Answer

In the private subnet(s) you need a route to the NAT Gateway. To do this, create a new VPC route table; create a default route (`0.0.0.0/0`) in that route table that has a destination of the NAT Gateway; then assign the route table to the private subnet(s). In the VPC you'll have two route tables: One for the public subnet(s) which has a default route to the Internet Gateway; and one for the private subnet(s).

How does a private subnet know how to route to a NAT gateway in the public subnet

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