Calico is an open source networking solution for OpenStack that provides tenant isolation, security groups, and external reachability constraints through network policy enforcement on every node in a cluster. The document outlines the basic steps to install and configure Calico in an Ubuntu environment, including installing OpenStack, configuring APT for Calico packages, adding the BIRD PPA, installing etcd, configuring Neutron to use the Calico plugin, and installing Calico services on controller and compute nodes. More detailed documentation for the Calico installation process can be found on Project Calico's website.