The Calendar List groups calendars by location:
iCloud calendars are type-specific. Each iCloud calendar can contain either Events or To Dos, but not both. BusyCal will indicate a To Do calendar by displaying a checkmark next to its name.
If you have a local, LAN, or Google calendar that you want to host on iCloud, you can move it to iCloud or merge it with an existing calendar on iCloud. See Hosting calendars on iCloud for more info.