This means flashoholics won’t have to go through the usual procedure of flashing CM10, but rather have the CM Updater take over the hassle. The OTA update feature is called CM Updater and is available only for stock CyanogendMod 10 releases. Sorry, custom ROMs.
You can also specify whether you want the updater to create a backup of your ROM in case things go south. After all, these are nightlies and everything could happen, so you better be safe than sorry.