Minikube applications can be accessed outside the host via port-forwarding. The applications hosted on Minikube have external cluster-IP address but the ip address is NAT'ed which means it is on a private network where the address is translated from the external IP address.
The external and cluster Ip address are two different layers of abstraction. The external in this case refers to the address that is visible only to the host since the minikube is hosted with a  only host visible network adapter. It has outbound external connectivity but no internal access except from what the host permits. The IP address does not route automatically to the pods within a minikube.
The cluster IP address refers to  one that has been marked cluster wide and is accessible outside the kubernetes cluster. It does not mean it is accessible over the NAT. It is different from the internal ip addresses used for the pods.
The layering therefore looks like the following:
 - Outside world
     -   Host (IP connectivity)
          - Minikube (Network Address Translation)
              - Cluster IP address ( Kubernetes )
                  - Pod IP address  ( Kubernetes )

The Minikube provides two features that enable transmission of data to the pod to and from the outside world.
This is called port-forwarding.
 To transmit the data to a web application serving at port 80, we can run the following commands on the host:
> kubectl port-forward pod/<podName> -n namespace 9880:80  for the inbound traffic
Forwarding from 80 -> 9880
and
> kubectl port-forward --address 0.0.0.0 pod/podName -n namespace for the outbound traffic from the application
Forwarding from 0.0.0.0:9880 -> 9000

It is important to recognize that the inbound and outbound rules must be specified separately for the same application. If the traffic involves both http and https then this results in a set of two rules for each kind of traffic - plain and encrypted.