XO Lite
XO Lite (Xen Orchestra Lite) is a lightweight version of Xen Orchestra for single-pool administration, served directly by your XCP-ng host just open https://your-host-ip (or its hostname), accept the self-signed certificate, and log in with the host's credentials (usually root and the password chosen during installation).
XO Proxy
XO Proxy is an architecture component you deploy in your infrastructure to locally handle the data streams of your Xen Orchestra backup jobs. The main Xen Orchestra Appliance stays in charge of configuring and orchestrating all backup jobs; the proxies execute them and carry the backup traffic.
XOSTOR
XOSTOR is the hyperconverged storage solution for XCP-ng: it turns the local disks of your hosts into a replicated, shared virtual SAN, with no dedicated external storage hardware. Technically, XOSTOR is a LinstorSR SMAPI driver developed by Vates, built on LINSTOR and DRBD from LINBIT, with a dedicated web UI in the Xen Orchestra Appliance for deployment and management.