LinuxTechi - https://www.linuxtechi.com/install-tripleo-undercloud-centos-7/
Undercloud is a single node OpenStack installation deployed either in a Virtual machine or in bare metal server. The objective of undercloud is to install, test, manage and update its overcloud servers (Controller, Compute & Storage nodes). In Red Hat terminology undercloud is known as “Director“. Undercloud basically contains all the images that is required to deployed Overcloud Controller, Computes, Swift and Storage.
Overcloud is the actual functional cloud for any organization where all the Virtual Machines are created on compute nodes and handle all the workloads. In other words we can say overcloud provides the openstack services like